Semiconductor memory

ABSTRACT

A semiconductor memory includes memory cells, a word line and bit lines of the memory cells, sense amplifiers connected to the bit lines, respectively, and a controller. Each sense amplifier includes first, second, and third transistors. The third transistor has one end connected to each of the first and second transistors, and the other end connected to a corresponding bit line. During a read operation, at a first time of a first period during which the controller applies a first read voltage to the word line, the controller applies a first voltage higher than ground voltage to the first transistor, and a second voltage to the second transistor. Also, at the first time, a first sense amplifier applies a voltage to a first bit line through its first and third transistors, and a second sense amplifier applies a voltage to a second bit line through tis second and third transistors.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/286,538, filed Feb. 26, 2019, which application is based upon andclaims the benefit of priority from Japanese Patent Application No.2018-151665, filed Aug. 10, 2018, the entire contents of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to a semiconductor memory.

BACKGROUND

A NAND flash memory capable of storing data in a nonvolatile manner isknown.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of asemiconductor memory according to a first embodiment.

FIG. 2 is a circuit diagram illustrating an example of a circuitconfiguration of a memory cell array in the semiconductor memoryaccording to the first embodiment.

FIG. 3 is a plan view illustrating an example of a planar layout of thememory cell array in the semiconductor memory according to the firstembodiment.

FIG. 4 is a plan view illustrating an example of a planar layout in acell area of the memory cell array in the semiconductor memory accordingto the first embodiment.

FIG. 5 is a cross-sectional view illustrating an example of across-sectional structure in the cell area of the memory cell array inthe semiconductor memory according to the first embodiment.

FIG. 6 is a cross-sectional view illustrating an example of across-sectional structure in a memory pillar in the semiconductor memoryaccording to the first embodiment.

FIG. 7 is a plan view illustrating an example of a planar layout in anextraction area of the memory cell array in the semiconductor memoryaccording to the first embodiment.

FIG. 8 is a cross-sectional view illustrating an example of across-sectional structure in the extraction area of the memory cellarray in the semiconductor memory according to the first embodiment.

FIG. 9 is a circuit diagram illustrating an example of a circuitconfiguration of a row decoder module in the semiconductor memoryaccording to the first embodiment.

FIG. 10 is a circuit diagram illustrating an example of a circuitconfiguration of a sense amplifier module in the semiconductor memoryaccording to the first embodiment.

FIG. 11 is a circuit diagram illustrating an example of a more detailedcircuit configuration of the sense amplifier module in the semiconductormemory according to the first embodiment.

FIG. 12 is a diagram illustrating an example of threshold voltagedistribution, data allocation, and read voltage of a memory celltransistor in the semiconductor memory according to the firstembodiment.

FIG. 13 is a timing chart illustrating an example of a read operation ofthe semiconductor memory according to the first embodiment.

FIG. 14 is a timing chart illustrating an example of a read operation ina modification example of the first embodiment.

FIG. 15 is a circuit diagram illustrating an example of a circuitconfiguration of a sense amplifier module in a semiconductor memoryaccording to a second embodiment.

FIG. 16 is a timing chart illustrating an example of a read operation ofthe semiconductor memory according to the second embodiment.

FIG. 17 is a timing chart illustrating an example of a read operation ina modification example of the second embodiment.

FIG. 18 is a circuit diagram illustrating an example of a circuitconfiguration of a sense amplifier module in a semiconductor memoryaccording to a third embodiment.

FIG. 19 is a timing chart illustrating an example of a read operation ina comparative example.

FIG. 20 is a table illustrating an example of setting of a kickoperation in the read operation of a semiconductor memory according to athird embodiment.

FIG. 21 is a timing chart illustrating an example of the read operationof the semiconductor memory according to the third embodiment.

FIG. 22 is a timing chart illustrating an example of a read operation ina modification example of the third embodiment.

FIG. 23 is a table illustrating an example of setting of a kickoperation in the read operation of a semiconductor memory according to afourth embodiment.

FIG. 24 is a timing chart illustrating an example of the read operationof the semiconductor memory according to the fourth embodiment.

FIG. 25 is a timing chart illustrating an example of a read operation ina modification example of the fourth embodiment.

FIG. 26 is a timing chart illustrating an example of a read operation ina first modification example.

FIG. 27 is a timing chart illustrating an example of a read operation ina second modification example.

DETAILED DESCRIPTION

Embodiments provide a semiconductor memory in which read operation isspeeded up.

In general, according to one embodiment, there is provided asemiconductor memory including first and second memory cells, wordlines, first and second bit lines, first and second sense amplifiers,and a controller. Each of the memory cells has a threshold voltagecorresponding to multi-bit data stored therein. The word line iselectrically connected to a gate of each of the first and second memorycells. The first and second bit lines are electrically connected to thefirst and second memory cells, respectively. The first and second senseamplifiers are electrically connected to the first and second bit lines,respectively, and each of the first and second sense amplifiers includesa first transistor, a second transistor, and a third transistor havingone end electrically connected to each of the first transistor and thesecond transistor, and the other end electrically connected to acorresponding bit line. During a read operation, the controller appliesa first read voltage to the word line, and at a first time of a firstperiod during which the controller applies the first read voltage to theword line, the controller applies a first voltage higher than a groundvoltage to the first transistor, and a second voltage different from thefirst voltage to the second transistor, and also at the first time, thefirst sense amplifier applies a voltage to the first bit line throughthe first transistor and the third transistor, and the second senseamplifier applies a voltage to the second bit line through the secondtransistor and the third transistor.

Hereinafter, embodiments will be described with reference to thedrawings. Each embodiment shows an example of an apparatus and a methodfor embodying the technical idea of the disclosure. The drawings areschematic or conceptual, and the sizes and ratios in the drawings arenot necessarily the same as the actual ones. The technical idea of thepresent disclosure is not limited to the shape, structure, arrangement,or the like of the elements illustrated in the drawings.

In the following description, elements having substantially the samefunction and configuration are given the same symbol. The numeralsfollowing the letters constituting the reference symbols are used todistinguish the elements having the same configuration. If there is noneed to distinguish the elements having reference symbols including thesame letter from each other, these elements are referred to using thereference symbols including only letters.

[1] First Embodiment

Hereinafter, a semiconductor memory 1 according to a first embodimentwill be described.

[1-1] Configuration of Semiconductor Memory 1 [1-1-1] OverallConfiguration of Semiconductor Memory 1

The semiconductor memory 1 is, for example, a NAND flash memory capableof storing data in a nonvolatile manner. The semiconductor memory 1 iscontrolled by, for example, an external memory controller 2. FIG. 1illustrates a configuration example of the semiconductor memory 1according to the embodiment.

As illustrated in FIG. 1, the semiconductor memory 1 includes, forexample, a memory cell array 10, a command register 11, an addressregister 12, a sequencer 13, a driver module 14, a row decoder module15, and a sense amplifier module 16.

The memory cell array 10 includes a plurality of blocks BLK0 to BLKn (nis an integer of 1 or more). The block BLK is a set of a plurality ofmemory cells capable of storing data in a nonvolatile manner, and isused as a data erase unit, for example.

Further, in the memory cell array 10, a plurality of bit lines and aplurality of word lines are provided. Each memory cell is associatedwith, for example, one bit line and one word line. The detailedconfiguration of the memory cell array 10 will be described later.

The command register 11 stores a command CMD received by thesemiconductor memory 1 from the memory controller 2. The command CMDincludes, for example, an instruction to cause the sequencer 13 toexecute a read operation, a write operation, an erase operation, and thelike.

The address register 12 stores address information ADD received by thesemiconductor memory 1 from the memory controller 2. The addressinformation ADD includes, for example, a block address BAd, a pageaddress PAd, and a column address CAd. For example, the block addressBAd, the page address PAd, and the column address CAd are used to selectthe block BLK, the word line, and the bit line, respectively.

The sequencer 13 controls the operation of the entire semiconductormemory 1. For example, the sequencer 13 controls the driver module 14,the row decoder module 15, the sense amplifier module 16, and the likebased on the command CMD stored in the command register 11 to execute aread operation, a write operation, an erase operation, and the like.

The driver module 14 generates a voltage to be used in a read operation,a write operation, an erase operation, and the like. Then, the drivermodule 14 applies the generated voltage to the signal line correspondingto the selected word line, for example, based on the page address PAdstored in the address register 12.

The row decoder module 15 selects one block BLK in the correspondingmemory cell array 10, based on the block address BAd stored in theaddress register 12. Then, the row decoder module 15 transfers, forexample, the voltage applied to the signal line corresponding to theselected word line, to the selected word line in the selected block BLK.

In the write operation, the sense amplifier module 16 applies a desiredvoltage to each bit line, in accordance with the write data DAT receivedfrom the memory controller 2. Further, in the read operation, the senseamplifier module 16 determines the data stored in the memory cell basedon the voltage of the bit line, and transfers the determination resultto the memory controller 2 as read data DAT.

Communication between the semiconductor memory 1 and the memorycontroller 2 supports, for example, the NAND interface standard. Forexample, in the communication between the semiconductor memory 1 and thememory controller 2, a command latch enable signal CLE, an address latchenable signal ALE, a write enable signal WEn, a read enable signal REn,a ready busy signal RBn, and an input/output signal I/O are used.

The command latch enable signal CLE is a signal indicating that theinput/output signal I/O received by the semiconductor memory 1 containsa command CMD. The address latch enable signal ALE is a signalindicating that the signal I/O received by the semiconductor memory 1contains address information ADD. The write enable signal WEn is asignal instructing the semiconductor memory 1 to handle the input/outputsignal I/O as an input signal. The read enable signal REn is a signalinstructing the semiconductor memory 1 to handle the input/output signalI/O as an output signal.

The ready busy signal RBn is a signal for notifying the memorycontroller 2 whether the semiconductor memory 1 is in a ready state inwhich it is ready to receive an instruction from the memory controller 2or in a busy state in which it is not ready to receive an instruction.The input/output signal I/O is, for example, an 8-bit width signal, andmay contain a command CMD, address information ADD, data DAT, and thelike.

The semiconductor memory 1 and the memory controller described above maybe packaged into a single semiconductor device by the combination ofthem. Examples of such a semiconductor device include a memory card suchas an SD™ card, a solid state drive (SSD), and the like.

[1-1-2] Circuit Configuration of Memory Cell Array 10

FIG. 2 shows an example of the circuit configuration of one block BLKamong a plurality of blocks BLK in the memory cell array 10 of thesemiconductor memory 1.

As illustrated in FIG. 2, the block BLK includes, for example, fourstring units SU0 to SU3. Each string unit SU includes a plurality ofNAND strings NS.

The plurality of NAND strings NS are associated with bit lines BL0 toBLm (m is an integer of 1 or more), respectively. Each NAND string NSincludes, for example, memory cell transistors MT0 to MT11, and selecttransistors ST1 and ST2.

The memory cell transistor MT includes a control gate and a chargestorage layer, and stores data in a nonvolatile manner. Each of theselect transistors ST1 and ST2 is used for selecting the string unit SUduring various operations.

In each NAND string NS, the memory cell transistors MT0 to MT11 areconnected in series between select transistors ST1 and ST2. In the sameblock BLK, the control gates of the memory cell transistors MT0 to MT11are commonly connected to the word lines WL0 to WL11, respectively.

In each NAND string NS, the drain of the select transistor ST1 isconnected to the associated bit line BL, and the source of the selecttransistor ST1 is connected to one end of the memory cell transistorsMT0 to MT11 connected in series. In the same block BLK, the gates of theselect transistors ST1 in the string units SU0 to SU3 are commonlyconnected to the select gate lines SGD0 to SGD3, respectively.

In each NAND string NS, the drain of the select transistor ST2 isconnected to the other end of the memory cell transistors MT0 to MT11connected in series. In the same block BLK, the sources of the selecttransistors ST2 are commonly connected to the source line SL, and thegates of the select transistors ST2 are commonly connected to the selectgate line SGS.

In the circuit configuration of the memory cell array 10 describedabove, the bit line BL is commonly connected across the plurality ofNAND strings NS corresponding to each block BLK, for example. The sourceline SL is commonly connected across a plurality of blocks BLK, forexample.

A set of a plurality of memory cell transistors MT connected to a commonword line WL in one string unit SU is referred to as a cell unit CU, forexample. For example, the storage capacity of the cell unit CU includingthe memory cell transistors MT each storing 1 bit data is defined as“one page data”. The cell unit CU may have a storage capacity of twopage data or more, according to the number of bits of data stored in thememory cell transistor MT.

In addition, the circuit configuration of the memory cell array 10 inthe semiconductor memory 1 according to the embodiment is not limited tothe configuration described above. For example, it may be designed suchthat the number of memory cell transistors MT and select transistors ST1and ST2 in each NAND string NS is any number. It may be designed suchthat the number of string units SU in each block BLK is any number.

[1-1-3] Structure of Memory Cell Array 10

Hereinafter, an example of the structure of the semiconductor memory 1according to the embodiment will be described.

In the drawings referred to below, an X direction corresponds to theextension direction of the word line WL, a Y direction corresponds tothe extension direction of the bit line BL, and a Z directioncorresponds to the vertical direction with respect to the surface of thesemiconductor substrate 20 on which the semiconductor memory 1 isformed.

Further, in the cross-sectional views referred to below, for ease ofviewing, elements such as insulating layers (interlayer insulatingfilms), wirings, and contacts are appropriately omitted. Further, in theplan views, hatching is appropriately added for ease of viewing. Thehatching added in the plan views is not necessarily related to thematerial or characteristics of the hatched elements.

Planar Layout of Memory Cell Array 10

FIG. 3 illustrates an example of a planar layout of eight blocks BLK0 toBLK7 of the memory cell array 10 in the semiconductor memory 1 accordingto the embodiment.

As illustrated in FIG. 3, each of the blocks BLK0 to BLK7 extends alongthe X direction. The blocks BLK0 to BLK7 are arranged in the Ydirection.

The area of the memory cell array 10 may be divided into, for example, acell area CA and hookup areas HA1 and HA2 (referred to herein asextraction areas). For example, the extraction areas HA1 and HA2 aredisposed at one end portion and the other end portion of the block BLKin the X direction, respectively. The cell area CA is disposed betweenthe extraction area HA1 and the extraction area HA2.

In the cell area CA, a plurality of NAND strings NS are formed. In eachof the extraction areas HA1 and HA2, a contact is formed forelectrically connecting each of the select gate lines SGD and SGS andthe word line WL connected to the NAND string NS to the row decodermodule 15.

Further, in the area where the block BLK is provided, for example, aplurality of slits SLT, SLTa, and SLTb are provided. For example, aninsulator is buried in each of the slits SLT, SLTa, and SLTb.

Each slit SLT is provided to extend from the extraction area HA1 to theextraction area HA2 along the X direction, and the plurality of slitsSLT are arranged in the Y direction. For example, one slit SLTa and twoslits SLTb are disposed between the adjacent slits SLT.

For example, the slits SLTa and SLTb are provided between the adjacentslits SLT and extend along the X direction, respectively. The two slitsSLTb are arranged in the extraction areas HA1 and HA2, respectively. Theslit SLTa is disposed between the slit SLTb in the extraction area HA1and the slit SLTb in the extraction area HA2.

In other words, between the adjacent slits SLT, for example, atransverse slit extending in the X direction and including the slitdividing portion DJ is provided. The transverse slit is divided by theslit dividing portion DJ in each of the extraction areas HA1 and HA2.

Among the divided transverse slits, the slit portion extending from theextraction area HA1 to the extraction area HA2 corresponds to the slitSLTa, and the slit portions respectively provided in the extraction areaHA1 and HA2 correspond to the slit SLTb.

The structure between the adjacent slits SLT described above correspondsto one block BLK, for example. It may be designed such that the numberof slits SLTa and SLTb disposed between the slits SLT is any number.Between the slits SLT, the slit dividing portion DJ is optional and maybe omitted.

Structure of Memory Cell Array 10 in Cell Area CA

FIG. 4 illustrates an example of a planar layout of one block BLK in thecell area CA of the memory cell array 10 in the semiconductor memory 1according to the first embodiment.

As illustrated in FIG. 4, in the cell area CA, the memory cell array 10includes, for example, a plurality of memory pillars MP and a pluralityof dummy pillars DMP. Between the slit SLT and the slit SLTa, forexample, a slit SHE is provided.

The slit SHE is provided to extend from the extraction area HA1 to theextraction area HA2 along the X direction. For example, an insulator isembedded in the slit SHE.

The dummy pillar DMP has a structure similar to, for example, the memorypillar MP, but is not used for storing data. The dummy pillar DMP isarranged, for example, so that the slit SHE partially overlies it.

The plurality of memory pillars MP are arranged, for example, in astaggered manner between the slit SLT and the slit SHE. Similarly, theplurality of memory pillars MP are arranged, for example, in a staggeredmanner between the slit SLTa and the slit SHE.

The memory pillar MP corresponds to, for example, one NAND string NS.For example, a set of a plurality of memory pillars MP provided betweenthe slit SLT and the slit SHE corresponds to one string unit SU.Similarly, a set of a plurality of memory pillars MP provided betweenthe slit SLTa and the slit SHE corresponds to another string unit SU.

Further, in the cell area CA, a plurality of bit lines BL and aplurality of contacts CP are provided in the memory cell array 10corresponding to the arrangement of the memory pillars MP.

The plurality of bit lines BL respectively extend in the Y direction andare arranged in the X direction. Each bit line BL is arranged so as tooverlie at least one memory pillar MP for each string unit SU. Forexample, two bit lines BL overlie each memory pillar MP.

The contact CP is disposed between one bit line BL among the pluralityof bit lines BL that overlie the memory pillar MP, and the memory pillarMP. Each memory pillar MP is electrically connected to a correspondingbit line BL via the contact CP.

The number of string units SU provided between the adjacent slits SLTmay be any number. The number and arrangement of the illustrated memorypillars MP is only an example, and the any number of memory pillars MPmay be provided in any arrangement. In addition, any number of bit linesBL may overlie each memory pillar MP.

FIG. 5 is a cross-sectional view of the memory cell array 10 taken alongthe line V-V in FIG. 4, showing an example of the sectional structure ofthe block BLK in the cell area CA.

As illustrated in FIG. 5, for example, conductors 21 to 25, the memorypillars MP, the dummy pillars DMP, the contacts CP, and the slits SLT,SLTa, and SHE are provided in the area corresponding to the cell areaCA.

A conductor 21 is provided above the semiconductor substrate 20 with aninsulating layer interposed therebetween. Although not illustrated,circuits such as the row decoder module 15 and the sense amplifiermodule 16 are provided in the insulating layer between the semiconductorsubstrate 20 and the conductor 21.

The conductor 21 is formed in a plate shape extending along the XYplane, for example, and is used as the source line SL.

A conductor 22 is provided on the conductor 21 with an insulating layerinterposed therebetween. The conductor 22 is formed in a plate shapeextending along the XY plane, for example, and is used as the selectgate line SGS.

On the conductor 22, an insulating layer and a conductor 23 arealternately stacked. The conductor 23 is formed in a plate shapeextending along the XY plane. For example, the plurality of stackedconductors 23 are used as word lines WL0 to WL11 sequentially from thesemiconductor substrate 20 side.

A conductor 24 is provided on the conductor 23 with an insulating layerinterposed therebetween. The conductor 24 is formed in a plate shapeextending along the XY plane, for example, and is used as the selectgate line SGD.

A conductor 25 is provided on the conductor 24 with an insulating layerinterposed therebetween. The conductor 25 is formed in a line shapeextending along the Y direction, for example, and is used as the bitline BL. That is, in an area not shown, a plurality of conductors 25 arearranged in the X direction.

The memory pillar MP is formed in a columnar shape extending along the Zdirection and penetrates, for example, the conductors 22 to 24. Forexample, the upper end of the memory pillar MP is placed in the layerbetween the layer provided with the conductor 24 and the layer providedwith the conductor 25. The lower end of the memory pillar MP is placedin a layer provided with the conductor 21, for example, and is incontact with the conductor 21.

Further, the memory pillar MP includes, for example, a core member 30, asemiconductor 31, and a stacked film 32. The core member 30 is, forexample, an insulator, and is formed in a columnar shape extending alongthe Z direction. The upper end of the core member 30 is placed in alayer above the layer provided with the conductor 24, for example. Thelower end of the core member 30 is placed in, for example, the layerprovided with the conductor 21.

The core member 30 is covered with the semiconductor 31. Thesemiconductor 31 is in electrical contact with the conductor 21 via theside surface of the memory pillar MP. The stacked film 32 covers theside surface and the lower surface of the semiconductor 31 except aportion where the conductor 21 and the semiconductor 31 are in contactwith each other.

Columnar contacts CP are provided on the semiconductor 31. A singleconductor 25, that is, one bit line BL is in contact with the uppersurface of the contact CP. The memory pillar MP and the conductor 25 maybe electrically connected via two or more contacts, or may beelectrically connected via other wirings.

The dummy pillar DMP is formed in a columnar shape extending along the Zdirection and penetrates, for example, the conductors 22 to 24. Thedetailed structure of the dummy pillar DMP is similar to the structureof the memory pillar MP, for example. However, the contact CP is notconnected to the dummy pillar DMP.

The slit SLT is formed in a plate shape extending along the XZ plane,for example, and divides the conductors 22 to 24. For example, the upperend of the slit SLT is placed in a layer between the layer including theupper end of the memory pillar MP and the layer provided with theconductor 25. The lower end of the slit SLT is placed in, for example,the layer provided with the conductor 21. The structure of the slit SLTais the same as the structure of the slit SLT, for example.

The slit SHE is provided to extend in the X direction, for example, anddivides the conductor 24. The slit SHE may divide a part of the dummypillar DMP. For example, the upper end of the slit SHE is placed in alayer between the layer including the upper end of the memory pillar MPand the layer provided with the conductor 25. The lower end of the slitSHE is placed in, for example, a layer between the uppermost conductor23 and the conductor 24. The slit SHE extending in the X direction maybe divided by the dummy pillar DMP at a position overlapping with thedummy pillar DMP.

FIG. 6 illustrates an example of the cross-sectional structure of thememory pillar MP in a section parallel to the surface of thesemiconductor substrate 20 and including the conductor 23.

As illustrated in FIG. 6, in the layer including the conductor 23, thecore member 30 is provided in the central portion of the memory pillarMP. The semiconductor 31 surrounds the side surface of the core member30. The stacked film 32 surrounds the side surface of the semiconductor31. The stacked film 32 includes, for example, a tunnel oxide film 33,an insulating film 34, and a block insulating film 35.

The tunnel oxide film 33 surrounds the side surface of the semiconductor31. The insulating film 34 surrounds the side surface of the tunneloxide film 33. The block insulating film 35 surrounds the side surfaceof the insulating film 34. The conductor 23 surrounds the side surfaceof the block insulating film 35.

In the configuration of the memory pillar MP described above, forexample, a portion where the memory pillar MP and the conductor 22 crosseach other functions as the select transistor ST2. A portion where thememory pillar MP and the conductor 23 cross each other functions as thememory cell transistor MT. A portion where the memory pillar MP and theconductor 24 cross each other functions as the select transistor ST1.

That is, the semiconductor 31 in the memory pillar MP functions as thechannel of each of the memory cell transistor MT and the selecttransistors ST1 and ST2. The insulating film 34 in the memory pillar MPfunctions as the charge storage layer of the memory cell transistor MT.

Structure of Memory Cell Array 10 in Extraction Area HA

FIG. 7 illustrates an example of a planar layout of the extraction areaHA1 of adjacent blocks BLK0 and BLK1 of the memory cell array 10 in thesemiconductor memory 1 according to the first embodiment. First, theplanar layout of the block BLK0 in the extraction area HA1 will bedescribed.

As illustrated in FIG. 7, in the area corresponding to the block BLK0 inthe extraction area HA1, the select gate line SGD (corresponding toconductor 24) is divided into four parts by the slits SLT, SLTa and SHE.The four-divided select gate lines SGD correspond to the string unitsSU0 to SU3, respectively.

The word lines WL0 to WL11 (corresponding to conductors 23) have aportion (in particular, terrace portion) which is not overlapped by aconductor of an upper layer. For example, the plurality of conductors 23respectively corresponding to the word lines WL0 to WL11 are provided inthree rows of stairs having two steps in the Y direction and havingmultiple steps formed in the X direction.

The slit dividing portion DJ is disposed, for example, in the terraceportion of the word line WL11. The word lines WL provided in the samelayer in the same block BLK are electrically connected together via theslit dividing portion DJ. The slit SLTb is arranged to penetrate all ofthe conductors 23 so as to divide the terrace portion of the word linesWL1, WL4, WL7, and WL10.

The select gate line SGS (corresponding to conductor 22) is drawn out inthe X direction from, for example, the end areas of the word lines WL0to WL2. The slit SLTb does not divide the select gate line SGS in theembodiments illustrated herein. The select gate line SGS provided ineach of the adjacent blocks BLK is divided by the slit SLT.

Further, in the area corresponding to the block BLK0, a contact CC isprovided, for example, in each of the terrace portions of the selectgate line SGS, the word lines WL0 to WL11, and the select gate line SGD.

The select gate line SGS, the word lines WL0 to WL11, and the selectgate line SGD of the block BLK0 are electrically connected to the rowdecoder module 15 via the corresponding contact CC provided in theextraction area HA1.

The planar layout of the block BLK1 in the extraction area HA1 is thesame as the layout obtained by inverting the planar layout of the blockBLK0 with the X direction as a symmetric axis and is depicted in FIG. 7without the contacts CC.

In this embodiment, the select gate line SGS, the word lines WL0 toWL11, and the select gate line SGD of the block BLK1 are alsoelectrically connected to the row decoder module 15 via the contacts CCprovided in the extraction area HA2.

Specifically, the planar layout of the blocks BLK0 and BLK1 in theextraction area HA2 is the same as, for example, those obtained byinverting the planar layout of the blocks BLK0 and BLK1 in theextraction area HA1 with the Y direction as the axis of symmetry, andproviding the contacts CC corresponding to the wiring in the block BLK1.

FIG. 8 is a cross-sectional view of the memory cell array 10 taken alongthe line VIII-VIII in FIG. 7, showing an example of the sectionalstructure of the block BLK in the extraction area HA. Further, in FIG.8, the arrangement of the slit SHE provided in the depth direction ofthe cross-sectional view is indicated by a broken line.

As illustrated in FIG. 8, for example, conductors 21 to 24, conductors40 and 41, and contacts CC and V1 are provided in an area correspondingto the block BLK0 in the extraction area HA1.

In the extraction area HA1, the end portion of the conductor 21corresponding to the source line SL does not extend into the extractionarea HA1 as far as the conductor 22 in the X direction, but is at leastwithin the cell area CA. The end portion of each of the conductor 22,the conductor 23, and the conductor 24 respectively corresponding to theselect gate line SGS, the word line WL, and the select gate line SGD hasa portion that is not overlapped by conductor of the upper layer.

The slit SHE is provided to divide the conductor 24 corresponding to theselect gate line SGD. Each contact CC is formed in a columnar shapeextending along the Z direction. The contact CC includes, for example, aconductor formed in a columnar shape.

Each of the conductors 40 and 41 is a wiring for connecting theconductors 22 to 24 drawn out from the cell area CA to the extractionarea HA1 to the row decoder module 15. The plurality of conductors 40are provided on the plurality of contacts CC, respectively.

A plurality of contacts V1 are provided on the plurality of conductors40, respectively. A plurality of conductors 41 are provided on theplurality of contacts V1, respectively. The conductors 40 and 41 may beconnected via a plurality of contacts, or different wirings may beconnected between the plurality of contacts.

In the structure of the block BLK0 in the extraction area HA1 describedabove, the wiring drawn out via the contact CC is electrically connectedto a circuit under the memory cell array 10 via, for example, an areaoutside the extraction area HA1.

The present disclosure is not limited to this, and the wiring drawn outvia the contact CC may be electrically connected, for example, via acontact penetrating a dummy block provided in the extraction area HA1,or a contact penetrating a wide terrace portion provided in theextraction area HA1, to a circuit under the memory cell array 10.

As described above, in the semiconductor memory 1 according to the firstembodiment, a voltage is applied to the word line WL (the conductor 23)via the contact CC connected to one side in the X direction. Dependingon the structure of the word line WL, the influence of RC delay of thewiring may not be ignored in the portion of the word line WL far fromthe connection point of the contact CC.

In the present specification, “RC delay” means the length of the RCdelay time from the time a voltage is applied to the wiring until thevoltage of the wiring rises to a target value. Further, in the followingdescription, the portion of the word line WL far from the connectionpoint of the contact CC is referred to as the “far end of the word lineWL”, and the portion of the word line WL closer to the connection pointof the contact CC is referred to as “near end of the word line WL”.

In the structure of the memory cell array 10 described above, the numberof conductors 23 is based on the number of the word lines WL. Aplurality of conductors 22 provided in a plurality of layers may beallocated to the select gate line SGS. In a case where the select gateline SGS is formed in a plurality of layers, a conductor different fromthe conductor 22 may be used. A plurality of conductors 24 provided in aplurality of layers may be allocated to the select gate line SGD.

[1-1-4] Circuit Configuration of Row Decoder Module 15

FIG. 9 illustrates an example of a circuit configuration of the rowdecoder module 15 in the semiconductor memory 1 according to the firstembodiment.

As illustrated in FIG. 9, the row decoder module 15 includes, forexample, row decoders RD0 to RDn. The row decoder RD is used forselecting the block BLK. The row decoders RD0 to RDn are associated withthe blocks BLK0 to BLKn, respectively.

The detailed circuit configuration of the row decoder RD will bedescribed below focusing on the row decoder RD0 corresponding to theblock BLK0.

The row decoder RD includes, for example, a block decoder BD, and highbreakdown voltage n-channel MOS transistors TR1 to TR13.

The block decoder BD decodes the block address BA. Then, the blockdecoder BD applies a predetermined voltage to the transfer gate line TGbased on the decoding result. The transfer gate line TG is commonlyconnected to the gates of the transistors TR1 to TR13. The transistorsTR1 to TR13 are connected between various signal lines wired from thedriver module 14 and various wirings of the associated block BLK.

Specifically, the driver module 14 is connected to signal lines SGDD0 toSGDD3, signal lines CG0 to CG7, and a signal line SGSD. The signal lineSGDD0 to SGDD3 correspond to the select gate lines SGD0 to SGD3,respectively. The signal lines CG0 to CG7 correspond to the word linesWL0 to WL7, respectively. The signal line SGSD corresponds to the selectgate line SGS.

One end of the transistor TR1 is connected to the signal line SGSD. Theother end of the transistor TR1 is connected to the select gate lineSGS. One ends of the transistors TR2 to TR9 are connected to the signallines CG0 to CG7, respectively. The other ends of the transistors TR2 toTR9 are connected to the word lines WL0 to WL7, respectively. One endsof the transistor TRIO to TR13 are connected to the signal lines SGDD0to SGDD3. The other ends of the transistor TRIO to TR13 are connected tothe select gate lines SGD0 to SGD3.

With the above configuration, the row decoder module 15 can select theblock BLK for executing various operations.

Specifically, during various operations, the block decoder BDcorresponding to the selected block BLK applies a voltage of “H” levelto the transfer gate line TG, and the block decoder BD corresponding tothe non-selected block BLK applies a voltage of “L” level to thetransfer gate line TG.

In the present specification, the “H” level is a voltage at which then-channel MOS transistor is turned on and the p-channel MOS transistoris turned off. The “L” level is a voltage at which the n-channel MOStransistor is turned off and the p-channel MOS transistor is turned on.

For example, when the block BLK0 is selected, the transistors TR1 toTR13 in the row decoder RD0 are turned on, and the transistors TR1 toTR13 in the other row decoders RD are turned off. In this case, acurrent path is formed between the various wirings provided in the blockBLK0 and the corresponding signal lines, and the current paths betweenthe various wirings provided in the other blocks BLKs and thecorresponding signal lines are cut off.

As a result, the voltage applied to each signal line by the drivermodule 14 is applied to various wirings provided in the selected blockBLK0 via the row decoder RD0. The row decoder module 15 can operate inthe same manner even when another block BLK is selected.

[1-1-5] Circuit Configuration of Sense Amplifier Module 16

FIG. 10 illustrates an example of a circuit configuration of the senseamplifier module 16 in the semiconductor memory 1 according to the firstembodiment.

As illustrated in FIG. 10, the sense amplifier module 16 includes, forexample, sense amplifier units SAU0 to SAUm. The sense amplifier unitsSAU0 to SAUm are respectively associated with bit lines BL0 to BLm.

Each sense amplifier unit SAU includes, for example, sense amplifierunit SA, and latch circuits SDL, ADL, BDL, and XDL. The sense amplifierunit SA, and the latch circuits SDL, ADL, BDL, and XDL are connected soas to be able to transmit and receive data to and from each other.

In a read operation, for example, the sense amplifier unit SA determineswhether the read data is “0” or “1”, based on the voltage of thecorresponding bit line BL. In other words, the sense amplifier unit SAsenses the data read out to the corresponding bit line BL and determinesthe data to be stored in the selected memory cell.

Each of the latch circuits SDL, ADL, BDL, and XDL temporarily storesread data, write data, and the like. The latch circuit XDL is connectedto an input/output circuit (not shown), and may be used for datainput/output between the sense amplifier unit SAU and the input/outputcircuit.

The latch circuit XDL can also function as a cache memory of thesemiconductor memory 1. For example, even if the latch circuits SDL,ADL, and BDL are in use, if the latch circuit XDL is empty, thesemiconductor memory 1 can be in a ready state.

FIG. 11 illustrates an example of a more detailed circuit configurationof the sense amplifier module 16 in the semiconductor memory accordingto the first embodiment.

As illustrated in FIG. 11, the sense amplifier unit SA includes, forexample, transistors 50 to 60, and a capacitor 61. The latch circuit SDLincludes, for example, transistors 70 and 71, and inverters 72 and 73.

For example, each of the transistors 50 and 52 is a p channel MOStransistor. Each of the transistors 51, 53 to 56, 58 to 60, 70, and 71is an n-channel MOS transistor. The transistor 57 is a high breakdownvoltage n-channel MOS transistor.

One end of the transistor 50 is connected to a power supply line. Thegate of the transistor 50 is connected to the node INV (SDL) of thelatch circuit SDL. For example, the power supply voltage Vdd is appliedto the power supply line connected to one end of the transistor 50.

One end of the transistor 51 is connected to the other end of thetransistor 50. The other end of the transistor 51 is connected to thenode ND1. A control signal BLX is input to the gate of the transistor51.

One end of each of the transistors 52 and 53 is connected to the nodeND1. The gate of each of the transistors 52 and 53 is connected to thenode INV (ADL) of the latch circuit ADL.

One ends of the transistors 54 and 55 are connected to the other ends ofthe transistors 52 and 53, respectively. The other end of each of thetransistors 54 and 55 is connected to the node ND2. Control signals BLC1and BLC2 are input to the gates of the transistors 54 and 55,respectively.

One end of the transistor 56 is connected to the node ND2. The other endof the transistor 56 is connected to the node SRC. The gate of thetransistor 56 is connected to the node INV (SDL) of the latch circuitSDL. For example, the ground voltage VSS is applied to the node SRC.

One end of the transistor 57 is connected to the node ND2. The other endof the transistor 57 is connected to the corresponding bit line BL. Acontrol signal BLS is input to the gate of the transistor 57.

One end of the transistor 58 is connected to the node ND1. The other endof the transistor 58 is connected to the node SEN. A control signal XXLis input to the gate of the transistor 58. One end of the transistor 59is grounded. The gate of transistor 59 is connected to the node SEN.

One end of the transistor 60 is connected to the other end of thetransistor 59. The other end of the transistor 60 is connected to thebus LBUS. A control signal STB is input to the gate of the transistor60. One end of the capacitor 61 is connected to the node SEN. A clockCLK is input to the other end of the capacitor 61.

In the latch circuit SDL, one end of each of the transistors 70 and 71is connected to the bus LBUS. The other ends of the transistors 70 and71 are connected to the nodes INV and LAT, respectively. Control signalsSTI and STL are input to the gates of the transistors 70 and 71,respectively.

The input node of the inverter 72 and the output node of the inverter 73are connected to the node LAT. The output node of the inverter 72 andthe input node of the inverter 73 are connected to the node INV.

The circuit configurations of the latch circuits ADL, BDL, and XDL arethe same as the circuit configuration of the latch circuit SDL, forexample. For example, in the latch circuit ADL, control signals ATI andATL are input to the gates of transistors 70 and 71, respectively. Ineach of the latch circuits BDL and XDL, a control signal different fromthat of the latch circuit SDL is input to each of the transistors 70 and71. Further, the nodes INV and LAT of each of the latch circuits SDL,ADL, BDL, and XDL are separately provided for each latch circuit.

Each of the control signals BLX, BLC1, BLC2, BLS, XXL, STB, STI, STL,ATI, and ATL described above is generated by, for example, the sequencer13. For example, the sequencer 13 can control the latch circuits SDL,ADL, BDL, and XDL, separately.

The timing at which the sense amplifier unit SA determines the data readout to the bit line BL is based on the timing at which the sequencer 13asserts the control signal STB. In the following description, “assertthe control signal STB” corresponds to temporary change of controlsignal STB from “L” level to “H” level by the sequencer 13.

[1-1-6] Data Allocation

FIG. 12 illustrates an example of threshold voltage distribution, a readvoltage, and a verify voltage of the memory cell transistor MT in thesemiconductor memory 1 according to the first embodiment. The verticalaxis of the threshold voltage distribution shown in FIG. 12 correspondsto the number of memory cell transistors MT, and the horizontal axiscorresponds to the threshold voltage Vth of the memory cell transistorMT.

As illustrated in FIG. 12, in the semiconductor memory 1 according tothe first embodiment, for example, eight types of threshold voltagedistribution are formed by the threshold voltages of the plurality ofmemory cell transistors MT in one cell unit CU.

In the present specification, the eight types of threshold voltagedistributions (corresponding to write levels) are respectively referredto as “ER” level, “A” level, “B” level, “C” level, “D” level, “E” level,“F” level, and “G” level, in order from the lowest threshold voltage.

Between adjacent threshold voltage distributions, a read voltage to beused in each read operation is set. For example, a read voltage AR isset between a maximum threshold voltage at “ER” level and a minimumthreshold voltage at “A” level.

Similarly, a read voltage BR is set between “A” level and “B” level. Aread voltage CR is set between “B” level and “C” level. A read voltageDR is set between “C” level and “D” level. A read voltage ER is setbetween “D” level and “E” level. A read voltage FR is set between “E”level and “F” level. A read voltage GR is set between “F” level and “G”level.

For example, when the read voltage AR is applied to the gate, the memorycell transistor MT is turned on when the threshold voltage thereof is at“ER” level, and the memory cell transistor MT is turned off when thethreshold voltage thereof is at “A” level or higher.

Similarly, when the read voltage BR is applied to the gate, the memorycell transistor MT is turned on when the threshold voltage thereof is at“A” level or lower, and the memory cell transistor MT is turned off whenthe threshold voltage thereof is at “B” level or higher. Even whenanother read voltage is applied to the gate, the memory cell transistorMT is turned on or off according to the threshold voltage.

A read pass voltage Vread is set at a voltage higher than the highestthreshold voltage distribution. Specifically, the read pass voltageVread is set to a voltage higher than the maximum threshold voltage atthe “G” level. When the read pass voltage Vread is applied to the gate,the memory cell transistor MT is turned on irrespective of data storedtherein.

Further, between adjacent threshold voltage distributions, a verifyvoltage to be used in each write operation is set. Specifically, verifyvoltages AV, BV, CV, DV, EV, FV, and GV are set corresponding to “A”level, “B” level, “C” level, “D” level, “E” level, “F” level, and “G”level, respectively.

The verify voltage AV is set between the maximum threshold voltage atthe “ER” level and the minimum threshold voltage at the “A” level and inthe vicinity of the “A” level. The verify voltage BV is set between themaximum threshold voltage at the “A” level and the minimum thresholdvoltage at the “B” level and in the vicinity of the “B” level.Similarly, other verify voltages are set in the vicinity of thecorresponding write level. That is, the verify voltages AV, BV, CV, DV,EV, FV, and GV are set to voltages slightly higher than the readvoltages AR, BR, CR, DR, ER, FR, and GR, respectively.

In the write operation, when the semiconductor memory 1 detects that thethreshold voltage of the memory cell transistor MT which stores certaindata exceeds the verify voltage corresponding to the data, thesemiconductor memory 1 completes the program of the memory celltransistor MT.

Different pieces of 3-bit data are allocated to the eight types ofthreshold voltage distribution of the memory cell transistor MTdescribed above. Below is an example of data allocation for thresholdvoltage distribution.

“ER” level: “111 (upper bit/middle bit/lower bit)” data

“A” level: “110” data

“B” level: “100” data

“C” level: “000” data

“D” level: “010” data

“E” level: “011” data

“F” level: “001” data

“G” level: “101” data.

When such data allocation is applied, one page data made up of lowerbits (lower page data) is determined by a read process using readvoltages AR, and ER. One page data made up of middle bits (middle pagedata) is determined by a read process using read voltages BR, DR, andFR. One page data made up of upper bits is determined by a read processusing read voltages CR and GR.

That is, the lower page data, the middle page data, and the upper pagedata are determined by the read process using two types, three types,and two types of read voltages, respectively. Such allocation of data isreferred to as “2-3-2 code”, for example. In the present specification,a case where the “2-3-2code” is applied to data allocation of the memorycell transistor MT will be described as an example.

[1-2] Read Operation of Semiconductor Memory 1

In the semiconductor memory 1 according to the first embodiment, in theread operation, the bit line BL that executes a kick operation and thebit line BL that does not execute the kick operation coexist.

The kick operation is a voltage applying method of temporarily settingthe driving voltage of the driver module 14 to a value higher than thetarget voltage value, and lowering the voltage to the target voltagevalue after elapse of a fixed time. The kick operation is executed forthe signal line CG and the control signal BLC, for example.

For example, when the kick operation is executed for the signal line CG,the voltage at the far end of the word line WL can reach the targetvoltage value quickly. When the kick operation is executed for thecontrol signal BLC, the amount of current supplied to the bit line BL bythe transistor to which the control signal BLC is input at the gate tocharge the bit line BL is increased.

Execution of the kick operation for the signal line CG is equivalent toexecution of a kick operation for the word line WL. Execution of thekick operation for the control signal BLC is equivalent to execution ofa kick operation for the bit line BL.

Therefore, in the present specification, the kick operation for thesignal line CG is also referred to as a kick operation for the word lineWL. The kick operation for the control signal BLC is also referred to asa kick operation for the bit line BL.

Further, in the following description, a voltage higher than the targetvoltage to be applied during the kick operation before the targetvoltage is applied is referred to as a kick voltage. A differencebetween the target voltage and the kick voltage in the kick operation isalso referred to as a kick amount. The memory cell transistor MT in thecell unit CU to be read is also referred to as a selected memory cell.The word line WL connected to the selected memory cell is referred to asa selected word line WLsel. The signal line CG connected to the selectedword line WLsel is referred to as a selected signal line CGsel.

An example of the read operation of the semiconductor memory 1 accordingto the first embodiment described below is a read operation of the lowerpage data.

FIG. 13 illustrates an example of a timing chart in the read operationof the lower page data in the semiconductor memory 1 according to thefirst embodiment.

In the read operation described below, a voltage is applied to theselected signal line CGsel by the driver module 14 and the row decodermodule 15. It is assumed that the node SEN is appropriately chargedduring a period in which each read voltage is applied.

The timing chart of FIG. 13 indicates the voltage of the bit line BL.The voltage of the bit line BL corresponds to the voltage applied to thegate of the transistor for clamping the voltage of the bit line BL minusthe threshold voltage of this transistor.

Further, it is assumed that the voltage of the node INV (SDL) of thelatch circuit SDL is set to “L” level. That is, during the period inwhich the read operation is executed, the transistor 50 is in an onstate and supplies the voltage to the transistor 51. Further, thetransistor 56 is in an off state and cuts off the current path betweenthe nodes ND2 and SRC.

As illustrated in FIG. 13, at the start of the read operation, therespective voltages of the selected signal line CGsel, the selected wordline WLsel, the control signals BLX, BLC1, BLC2, and XXL, and the bitline BL are, for example, a ground voltage Vss. The respective voltagesof the node INV (ADL) and the control signal STB are, for example, “L”level.

When the voltage of the node INV (ADL) is “L” level, the transistor 52is turned on and the transistor 53 is turned off. That is, the currentpath between the nodes ND1 and ND2 is set as a path through thetransistors 52 and 54.

When the read operation of the lower page data is started, the sequencer13 executes an operation of removing residual electrons in the channel,for example, in the period from the time t0 to the time t1. In theperiod from the time t1 to the time t4, the sequencer 13 executes a readprocess using the read voltage AR. In the period from the time t4 to thetime t7, the sequencer 13 executes a read process using the read voltageER.

Specifically, at time t0, for example, the read pass voltage Vread isapplied to the selected signal line CGsel together with the non-selectedsignal lines. Then, the voltage of the selected word line WLsel risesbased on the voltage applied to the selected signal line CGsel. At thesame time, although not shown in FIG. 13, the voltages of thenon-selected word lines rises based on the voltages applied to thenon-selected signal lines.

For example, the voltage (“Near” in FIG. 13) at the near end of theselected word line WLsel rises to the read pass voltage Vread, similarlyto the selected signal line CGsel, and the voltage (“Far” in FIG. 13) atthe far end of the selected word line WLsel is delayed from the selectedsignal line CGsel, and rises to the read pass voltage Vread.

Further, at time t0, for example, the sequencer 13 raises the voltage ofthe control signal BLX from Vss to VblxL, and raises the respectivevoltages of the control signals BLC1 and BLC2 from Vss to VblcL. Thevoltage value VblcL is, for example, lower than VblxL.

At this time, since the voltage of the node INV (ADL) is “L” level, thevoltage clamped by the transistors 52 and 54 is applied to the bit lineBL. Then, the voltage of the bit line BL rises from Vss to VblcL,similarly to the control signal BLC1, for example.

When the voltage of the selected word line WLsel rises to Vread and therespective voltages of the control signals BLC1 and BLC2 rise from Vssto VblcL, the transistors in the NAND string NS are turned on, andresidual electrons in the channel of the NAND string NS are removed.

Next, at time t1, the read voltage AR is applied to the selected signalline CGsel. Then, the voltage of the selected word line WLsel fallsbased on the voltage applied to the selected signal line CGsel.Specifically, for example, the voltage at the near end of the selectedword line WLsel falls to the read voltage AR similarly to the selectedsignal line CGsel, and the voltage at the far end of the selected wordline WLsel falls to the read voltage AR, with a delay from the selectedsignal line CGsel.

Further, at time t1, the sequencer 13 raises the voltage of the controlsignal BLX, for example, from VblxL to Vblx, and sets the voltage of thenode INV (ADL) to “H” level. Then, the voltage at the node ND1 rises tothe voltage clamped by the transistor 51. When the voltage of the nodeINV (ADL) is “H” level, the transistor 52 is turned off, and thetransistor 53 is turned on. That is, a current path between the nodesND1 and ND2 is set to a path through the transistors 53 and 55, and avoltage based on the control signal BLC2, for example, is applied to thebit line BL.

Next, at time t2, the sequencer 13 raises the voltages of the controlsignals BLC1 and BLC2 from VblcL to Vblc. At this time, the sequencer 13executes a kick operation for the control signal BLC1. The voltage valueVblc is, for example, lower than Vblx.

Specifically, the kick voltage Vblk is first applied to the signal lineto which the control signal BLC1 is supplied, and Vblc is applied afterthe kick voltage Vblk is applied for a short time. The kick voltage Vblkis higher than Vblc, and the difference between Vblk and Vblccorresponds to the kick amount Dblk.

Since the voltage of the node INV (ADL) is “H” level at the time t2, thevoltage clamped by the transistors 53 and 55 is applied to the bit lineBL. As a result, the voltage of the bit line BL is controlled by thecontrol signal BLC2 to rise to a voltage based on Vblc. As thetransistor 52 is turned off, a voltage based on the kick voltage Vblk isprevented from being applied to the bit line.

Further, while the read voltage AR is applied to the selected word lineWLsel, the voltage of the bit line BL changes according to the state ofthe selected memory cell. Specifically, the selected memory cell isturned on or off according to the threshold voltage and read voltage.

For example, when the selected memory cell is in an on state, thevoltage of the bit line BL falls below the voltage of the bit line BL ofthe off-cell (on-cell in FIG. 13). When the selected memory cell is inan off state, the voltage of the bit line BL maintains the voltage basedon Vblc (off-cell in FIG. 13).

Next, at time t3, the sequencer 13 raises the voltage of the controlsignal XXL from Vss to Vxxl. When the voltage of the control signal XXLrises to Vxxl, the transistor 58 is turned on. Then, the voltage of thenode SEN changes according to the voltage of the bit line BL.

Then, after the voltage of the bit line BL is reflected on the node SEN,the sequencer 13 lowers the voltage of the control signal XXL from Vxxlto Vss. When the voltage of the control signal XXL falls to Vss, thetransistor 58 is turned off and the voltage of the node SEN is fixed.

Thereafter, the sequencer 13 asserts the control signal STB anddetermines the data to be stored in the selected memory cell.Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage AR, and stores the determination resultin the latch circuit BDL, for example.

Then, the sequencer 13 changes the voltage of the node INV (ADL) in thelatch circuit ADL, based on the data retained in the latch circuit BDL.In other words, the sequencer 13 sets the current path between the nodesND1 and ND2, based on the read result according to the read voltage AR.

For example, when the latch circuit BDL stores data corresponding to theoff-cell, the sequencer 13 sets the voltage of the node INV (ADL) to “L”level. When the latch circuit BDL stores data corresponding to theon-cell, the sequencer 13 sets the voltage of the node INV (ADL) to “H”level.

That is, in the sense amplifier unit SAU corresponding to the selectedmemory cell in which the off state is maintained by the read voltage AR,the current path between the nodes ND1 and ND2 is set as a path throughthe transistors 52 and 54. In the sense amplifier unit SAU correspondingto the selected memory cell which is turned on by the read voltage AR,the current path between the nodes ND1 and ND2 is set as a path throughthe transistors 53 and 55.

Next, at time t4, the read voltage ER is applied to the selected signalline CGsel. At this time, the sequencer 13 executes a kick operation forthe selected signal line CGsel. Specifically, the kick voltage isapplied to the selected signal line CGsel for a short time before theread voltage ER is applied. The kick voltage for the selected signalline CGsel corresponds to the voltage obtained by adding the kick amountDcgk for the selected signal line CGsel to the target read voltage, forexample.

Then, the voltage of the selected word line WLsel rises based on thevoltage applied to the selected signal line CGsel. Specifically, forexample, the voltage at the near end of the selected word line WLselreaches the read voltage ER after the kick voltage is applied, similarlyto the selected signal line CGsel. The voltage at the far end of theselected word line WLsel reaches the read voltage ER without exceedingthe read voltage ER due to the influence of the RC delay of the wiring,for example.

Next, at time t5, the sequencer executes a kick operation for thecontrol signal BLC1. Specifically, the kick voltage Vblk is firstapplied to the signal line to which the control signal BLC1 is supplied,and Vblc is applied after the kick voltage Vblk is applied for a shorttime.

Since the voltage of the node INV (ADL) is “L” level at the time t5, thevoltage clamped by the transistors 52 and 54 is applied to the bit lineBL. Then, the voltage of the bit line BL changes to a voltage based onVblc (“BLC1” in FIG. 13), after a voltage based on the kick voltage Vblkis applied for a short time, corresponding to the control signal BLC1,for example.

Since the voltage of the node INV (ADL) is “H” level at the time t5, thevoltage clamped by the transistors 53 and 55 is applied to the bit lineBL. Then, the voltage of the bit line BL maintains a voltage based onthe Vblc, corresponding to the control signal BLC2, for example (“BLC2”in FIG. 13).

Thereafter, the voltage of the bit line BL changes depending on thestate of the selected memory cell to which the read voltage ER isapplied. Since the voltage change of the bit line BL is the same as thereadout process by the read voltage AR described at the time t 2, itsdescription will be omitted.

Next, at time t6, the sequencer 13 raises the voltage of the controlsignal XXL from Vss to Vxxl. When the voltage of the control signal XXLrises to Vxxl, the transistor 58 is turned on. Then, the voltage of thenode SEN changes according to the voltage of the bit line BL.

Then, after the voltage of the bit line BL is reflected on the node SEN,the sequencer 13 lowers the voltage of the control signal XXL from Vxxlto Vss. When the voltage of the control signal XXL falls to Vss, thetransistor 58 is turned off and the voltage of the node SEN is fixed.

Thereafter, the sequencer 13 asserts the control signal STB anddetermines the data to be stored in the selected memory cell.Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage ER.

Then, the sequencer 13 determines the lower page data based on thedetermination result and the read result based on the read voltage ARstored in the latch circuit BDL, and supplies the determined lower pagedata to, for example, the latch circuit XDL.

Next, at time t7, the sequencer 13 returns each of the selected signalline CGsel, and the control signals BLX, BLC1, BLC2, and XXL to thestate before the read operation, and finishes the read operation of thelower page data. When the memory controller 2 detects that thesemiconductor memory 1 completes the read operation of the lower pagedata, the memory controller 2 causes the semiconductor memory 1 tooutput the lower page data.

As described above, the semiconductor memory 1 according to the firstembodiment can execute the read operation of the lower page data.Incidentally, in the semiconductor memory 1 according to the firstembodiment, in the read operation of each of the middle page data andthe upper page data, similarly to the read operation of the lower pagedata, the kick operation can be appropriately executed according to theread result.

[1-3] Effect of First Embodiment

In the semiconductor memory 1 according to the first embodimentdescribed above, it is possible to speed up the read operation of thesemiconductor memory 1. The effect of the semiconductor memory 1according to the first embodiment will be described in detail below.

In a semiconductor memory in which memory cells are three-dimensionallystacked, a conductor (e.g., word line WL) used as a gate electrode of amemory cell and an interlayer insulating film are alternately stacked,so a volume increase is achieved by increasing the number of stackedlayers.

The stacked word lines WL are drawn in a stepwise shape, for example, atthe end portion of the memory cell array, and a voltage is applied viathe contacts connected to the terrace portions of the formed staircase.However, the word line WL having such a structure tends to have a largeRC delay when a voltage is applied.

For example, it may be assumed that the rising speed of the voltage isdifferent between an area close to the driver (near end of the word lineWL) and an area far from the driver (far end of the word line WL), andthe voltage at the far end of the word line WL reaches a target voltagewith a delay greater than the voltage at the near end of the word lineWL.

Therefore, in the semiconductor memory, for example, in order to assistthe voltage rise at the far end of the word line WL, the kick operationfor the word line WL is executed. When the kick operation for the wordline WL is executed, the voltage at the far end of the word line WLreaches the target voltage earlier than when the kick operation is notexecuted.

However, when the kick operation for the word line WL is executed,overdischarge occurs in the bit line BL connected to the NAND string NScorresponding to the near end portion of the word line WL, and time forstabilizing the voltage of the bit line BL may be prolonged.

In addition, as described above, the voltage of the selected word lineWLsel is raised to the read pass voltage Vread at the start of the readoperation in order to remove residual electrons in the channel of theNAND string NS, and then is caused to fall toward the read voltage AR.As the falling speed of the voltage is different between the area closeto the driver (near end of the word line WL) and the area far from thedriver (far end of the word line WL), and the voltage remains larger atthe far end of the word line WL as compared with the voltage at the nearend of the word line WL. As a result, overdischarge occurs in the bitline BL connected to the NAND string NS corresponding to the far endportion of the word line WL, and time for stabilizing the voltage of thebit line BL may be prolonged.

In the other words, overdischarge occurs in the bit line BL when thevoltage of the word line WL is caused to first overshoot and then fallto its target level.

As a countermeasure against overdischarge of the bit line BL, it isconceivable to charge the bit line BL in which overdischarge occurs byexecuting the kick operation for the bit line BL. Thus, charging of theoverdischarged bit line BL is assisted, and the voltage of the bit lineBL can be stabilized in a short time.

Further, it may be assumed that in the kick operation for the bit lineBL, the effect changes depending on whether the memory cell to which theread voltage is applied is in the on state or the off state in the readprocess in which the kick operation is executed.

For example, when the threshold voltage of the memory cell to which theread voltage is applied is larger than the read voltage, when thesequencer 13 reflects the voltage of the bit line BL on the node SEN,the voltage of the bit line BL needs to be a voltage of “H” level. Inother words, when the memory cell to which the read voltage is appliedis in the off state, it is preferable that the voltage of the bit lineBL is maintained in a high state.

That is, in each read process, the bit line BL connected to a memorycell which is turned off (hereinafter, referred to as an off-cell) isgreatly affected by overdischarge on the bit line BL, which may causeerroneous reading. Therefore, it is preferable that the kick operationis executed for the bit line BL connected to the memory cell which isclearly turned off.

On the other hand, when the threshold voltage of the memory cell towhich the read voltage is applied is the read voltage or less, when thevoltage of the bit line BL is reflected on the node SEN, the voltage ofthe bit line BL needs to be a voltage of “L” level. In other words, whenthe memory cell to which the read voltage is applied is turned on, it ispreferable that the voltage of the bit line BL transitions to a lowstate.

That is, in each read process, the bit line BL connected to a memorycell which is turned on (hereinafter, referred to as an on-cell) haslittle influence due to overdischarge on the bit line BL. Therefore, itis preferable that the kick operation is omitted for the bit line BLconnected to the memory cell which is clearly turned on.

Further, in each read process, when the kick operation is executed forthe bit line BL connected to the on-cell, the variation in the voltageof the bit line BL increases. In this case, it may be assumed that thevoltage of the bit line BL adjacent to the bit line BL connected to theon-cell is lowered by capacitive coupling. For example, when the bitline BL connected to the on-cell is adjacent to the bit line BLconnected to the off-cell, the voltage of the bit line BL connected tothe off-cell is lowered, and erroneous reading is performed on the bitline BL connected to the off-cell may occur.

Therefore, in the semiconductor memory 1 according to the firstembodiment, in the read operation, the kick operation for the bit lineBL that can be determined to be in an on state in advance is omitted.

This operation may be implemented by the circuit configuration of thesense amplifier unit SAU described with reference to FIG. 11, forexample. Specifically, the state of the memory cell transistor MT in thelast read process is stored in the node INV (ADL) of the latch circuitADL, for example.

For example, when the read process is executed in the order of the readvoltages AR and ER, it is clear that the memory cell transistor MT whichis turned on by the read voltage AR is turned on by the read voltage ER.At this time, the sequencer 13 sets the voltage of the node INV (ADL),for example, to “H” level.

On the other hand, it is not determined whether the memory celltransistor MT which is turned off by the read voltage AR is to be turnedon or turned off by the read voltage ER. At this time, the sequencer 13sets the voltage of the node INV (ADL), for example, to “L” level.

The node INV (ADL) is connected to the gate of the p-channel MOStransistor 52 and the gate of the n-channel MOS transistor 53, forexample. The transistor 52 is placed, for example, in a current path inwhich a kick operation is executed, and the transistor 53 is placed, forexample, in a current path in which a kick operation is not executed.That is, one of the transistors 52 and 53 is turned on and the other isturned off, based on the voltage of the node INV (ADL).

Thus, in the semiconductor memory 1 according to the first embodiment,it is possible to selectively omit the kick operation for the bit lineBL that can be determined to be in an on state in advance.

As a result, in the semiconductor memory 1 according to the firstembodiment, it is possible to prevent erroneous reading caused byperforming the kick operation for the bit line BL connected to theon-cell. In the semiconductor memory 1 according to the firstembodiment, the stabilization time of the bit line BL can be shortenedby appropriately executing the kick operation for the bit line BL, theread operation can be speeded up.

When read voltages are applied in order from the lowest read voltage, itis considered that the number of memory cell transistors MT to be turnedon by the read voltage applied first is smaller than the number ofmemory cell transistors MT to be turned on by the read voltage appliedlater.

In other words, it may be assumed that the number of off-cells is largerthan the number of on-cells, in the read process at the first appliedread voltage. Since the number of off-cells is large, it may be assumedthat the number of off-cells affected by noise by the bit line BLconnected to the on-cell increases.

Therefore, the semiconductor memory 1 according to the first embodimentomits the kick operation for all the bit lines BL, for example, in thefirst read process. Further, in the semiconductor memory 1 according tothe first embodiment, in the second and subsequent read processes, forexample, the kick operation is omitted for the bit line BL correspondingto the memory cell transistor MT of which being turned on is clear,similar to the first read process.

Thus, in the semiconductor memory 1 according to the first embodiment,it is possible to reduce the number of error bits and improve thereliability of data.

In the second and subsequent read processes, for example, in a casewhere the read voltage is higher than the predetermined voltage, it maybe assumed that the number of on-cells becomes dominant. Therefore, inthe second and subsequent read processes out of the read operations, thesequencer 13 may execute the kick operation for the bit line BLcorresponding to the memory cell transistor MT of which being turned onis not clear, according to the read voltage to be applied.

[1-4] Modification Example of First Embodiment

In the semiconductor memory 1 according to the first embodimentdescribed above, the read operation in which read voltages are appliedin order from the lowest read voltage is given as an example, but thepresent disclosure is not limited thereto. For example, the operationdescribed in the first embodiment can be applied, even in the case wherethe read voltage is applied from the highest read voltage.

Hereinafter, an example of a read operation in the modification exampleof the first embodiment will be described.

FIG. 14 illustrates an example of a timing chart in the read operationof the lower page data in the modification example of the firstembodiment.

As illustrated in FIG. 14, in the read operation in the modificationexample of the first embodiment, the order in which the read voltage isapplied is switched for the read operation in the first embodimentdescribed with reference to FIG. 13.

That is, in the read operation of the modification example of the firstembodiment, at time t1, the read voltage ER is applied to the selectedsignal line CGsel. At time t4, the read voltage AR is applied to theselected signal line CGsel. When each read voltage is applied to theselected signal line CGsel, the voltage at the near end (“Near” in FIG.14) of the selected word line WLsel falls similarly to the selectedsignal line CGsel, and the voltage at the far end (“Far” in FIG. 14) ofthe selected word line WLsel falls with a delay from the selected signalline CGsel.

As described above, the voltage of the selected word line WLsel fallsfrom the read pass voltage Vread to the read voltage ER at time t1, andfalls from the read voltage ER to the read voltage AR at time t4. Inaddition, due to the difference in voltage falling speed between thearea close to the driver (near end of the word line WL) and the area farfrom the driver (far end of the word line WL), the voltage remainslarger at the far end of the word line WL as compared with the voltageat the near end of the word line WL. As a result, overdischarge occursin the bit line BL connected to the NAND string NS corresponding to thefar end portion of the word line WL, and time for stabilizing thevoltage of the bit line BL may be prolonged.

Also in the modification example of the first embodiment, the kickoperation for the bit line BL is performed as a countermeasure againstoverdischarge of the bit line BL.

Specifically, in the read operation in the modification example of thefirst embodiment, in the first kick operation, the kick operation forall the bit lines BL is executed.

Specifically, at time t1, the sequencer 13 sets the voltage of the nodeINV (ADL) to “L” level. When the voltage of the node INV (ADL) is “L”level, the transistor 52 is turned on and the transistor 53 is turnedoff. That is, a current path between the nodes ND1 and ND2 is set to apath through the transistors 52 and 54, and a voltage based on thecontrol signal BLC1, for example, is applied to the bit line BL.

Therefore, at time t2, a voltage corresponding to the control signalBLC1 on which the kick operation is executed is applied to the bit lineBL. That is, at time t2, the voltage of the bit line BL changes to avoltage based on Vblc, after a voltage based on the kick voltage Vblk isapplied for a short time, corresponding to the control signal BLC1, forexample.

Since the other operations of the read operation in the modificationexample of the first embodiment are similar to the read operation in thefirst embodiment, a description thereof will be omitted. While the readoperation of the lower page data is shown as the modification example ofthe first embodiment, the same operation may be executed for the readoperation of each of the middle page data and the upper page data.

As described above, in the read operation in the modification example ofthe first embodiment, the kick operation is executed for the bit line BLthat can be determined to be in an off state in advance.

For example, in a case where the read process is executed in the orderof the read voltages ER and AR, it is clear that the memory celltransistor MT which is turned off by the read voltage ER is turned offby the read voltage AR. At this time, the sequencer 13 sets the voltageof the node INV (ADL), for example, to “L” level.

On the other hand, it is not determined whether the memory celltransistor MT which is turned on by the read voltage ER is to be turnedon or turned off by the read voltage AR. At this time, the sequencer 13sets the voltage of the node INV (ADL), for example, to “H” level.

In the read operation in the modification example of the firstembodiment, similarly to the first embodiment, whether or not to executethe kick operation for the bit line BL can be set based on the voltageof the node INV (ADL).

Thus, in the read operation in the modification example of the firstembodiment, the kick operation can be selectively executed for the bitline BL that can be determined to be in an off state in advance.

As a result, in the read operation in the modification example of thefirst embodiment, it is possible to prevent erroneous reading caused bynot performing the kick operation for the bit line BL connected to theoff-cell. In the read operation in the modification example of the firstembodiment, the stabilization time of the bit line BL can be shortenedby appropriately executing the kick operation for the bit line BL, andthe read operation can be speeded up.

In a case where read voltages are applied in order from the highest readvoltage, it is considered that the number of memory cell transistors MTto be turned on by the read voltage applied first is larger than thenumber of memory cell transistors MT to be turned on by the read voltageapplied later.

In other words, it may be assumed that the number of on-cells is largerthan the number of off-cells, in the read process at the first appliedread voltage. Since the number of on-cells is large, it may be assumedthat the number of off-cells affected by noise by the bit line BLconnected to the on-cell decreases.

Thus, in the read operation in the modification example of the firstembodiment, for example, the first kick operation is executed for allthe bit lines BL. Further, in the read operations in the modificationexample of the first embodiment, in the second and subsequent readprocesses, for example, the kick operation is executed for the bit lineBL corresponding to the memory cell transistor MT of which being turnedoff is not clear, similar to the first read operation.

Thus, in the read operation in the modification example of the firstembodiment, it is possible to reduce the number of error bits andimprove the reliability of data.

In the second and subsequent read processes, for example, in a casewhere the read voltage is lower than the predetermined voltage, it maybe assumed that the number of off-cells becomes dominant. Therefore, inthe second and subsequent read processes out of the read operations, thesequencer 13 may omit a kick operation for the bit line BL correspondingto the memory cell transistor MT of which being turned off is not clear,according to the read voltage to be applied.

[2] Second Embodiment

A semiconductor memory 1 according to a second embodiment executes aread operation similar to that of the first embodiment, by using a senseamplifier module 16 different from that of the first embodiment. Withrespect to the semiconductor memory 1 according to the secondembodiment, different features from that of the first embodiment will bedescribed below.

[2-1] Circuit Configuration of Sense Amplifier Module 16

FIG. 15 illustrates an example of the circuit configuration of the senseamplifier module 16 in the semiconductor memory according to the secondembodiment, by extracting one sense amplifier unit SAU out of aplurality of sense amplifier units SAU in the sense amplifier module 16.

As illustrated in FIG. 15, a sense amplifier unit SA in the secondembodiment has a configuration in which transistors 51 to 55, and 58 areomitted from the sense amplifier unit SA described with reference toFIG. 11 in the first embodiment and transistors 80 to 84 are addedthereto.

For example, each of the transistors 80 to 82 and 84 is an n-channel MOStransistor. The transistor 83 is a p-channel MOS transistor.

One end of the transistor 80 is connected to the other end of thetransistor 50. The other end of the transistor 80 is connected to thenode ND2. A control signal BLX1 is input to the gate of the transistor80.

The transistor 81 is connected to one end of the transistor 57 and thenode ND2. Specifically, one end of the transistor 81 is connected to thenode ND2, and the other end of the transistor 81 is connected to one endof the transistor 57. A control signal BLC1 is input to the gate of thetransistor 81.

One end of the transistor 82 is connected to the node ND2. The other endof the transistor 82 is connected to the node SEN. A control signal BLC2is input to the gate of the transistor 82.

One end of the transistor 83 is connected to a power supply line. Thegate of the transistor 83 is connected to the bus LBUS. For example, thepower supply voltage Vdd is applied to the power supply line connectedto one end of the transistor 83.

One end of the transistor 84 is connected to the other end of thetransistor 83. The other end of the transistor 84 is connected to thenode SEN. A control signal BLX2 is input to the gate of the transistor84.

Since the other configurations of the semiconductor memory 1 accordingto the second embodiment are similar to, for example, the semiconductormemory 1 according to the first embodiment, the explanation is omitted.

[2-2] Read Operation of Semiconductor Memory 1

FIG. 16 illustrates an example of a timing chart in the read operationof the lower page data in the semiconductor memory 1 according to thesecond embodiment. In the read operation in the second embodiment, it isdefined that the transistor 50 is in an on state similarly to the firstembodiment and supplies a voltage to the transistor 80.

As illustrated in FIG. 16, at the start of the read operation, therespective voltages of the selected signal line CGsel, the selected wordline WLsel, the control signals BLX1, BLX2, BLC1, and BLC2, and the bitline BL are, for example, a ground voltage Vss. The voltage of thecontrol signal STB is, for example, “L” level.

When the read operation of the lower page data is started, the sequencer13 executes an operation of removing residual electrons in the channel,for example, in the period from the time t0 to the time t1, similarly tothe first embodiment. In the period from the time t1 to the time t5, thesequencer 13 executes a read process using the read voltage AR. In theperiod from the time t5 to the time t9, the sequencer 13 executes a readprocess using the read voltage ER.

Specifically, at time to, a read pass voltage Vread, for example, isapplied to the selected signal line CGsel. Then, the voltage of theselected word line WLsel rises based on the voltage applied to theselected signal line CGsel.

Further, at time t0, for example, the sequencer 13 raises the voltage ofeach of the control signals BLX1, BLC1, and BLC2 from Vss to VblcL, andraises the voltage of the control signal BLX2 from Vss to VblxL.

At this time, the voltage clamped by the transistors 80 and 81, forexample, is applied to the bit line BL. Then, the voltage of the bitline BL rises from Vss to a voltage based on VblcL, for example,corresponding to the control signal BLC1.

Next, at time t1, the read voltage AR is applied to the selected signalline CGsel. Then, the voltage of the selected word line WLsel fallsbased on the voltage applied to the selected signal line CGsel.

Further, at time t1, the sequencer 13 sets the voltage of the bus LBUSto “H” level, raises the voltage of the control signal BLX1 from VblcLto Vblc, and changes the voltage of the control signal BLX2 from VblxLto Vblx, for example.

When the voltage of the bus LBUS is set to the “H” level, the transistor83 is turned off, and the supply of the voltage to the transistor 84 isinterrupted. Further, the voltage at the node ND2 rises to the voltageclamped by the transistor 80.

Next, at time t2, the sequencer 13 executes the kick operation for eachof the control signals BLC1 and BLC2, for example. Specifically, thesequencer 13 raises the voltage of the control signal BLC1 to the kickvoltage VblkH, and raises the voltage of the control signal BLC2 to thekick voltage Vblk. The kick voltage VblkH is higher than Vblk.

While the kick operation is executed for each of the control signalsBLC1 and BLC2, a voltage due to a path passing through the transistors50, 80, and 81 is applied to the bit line BL. Then, a voltage based onVblc is applied to the bit line BL for a short time, corresponding tothe control signal BLX1, for example.

Then, the sequencer 13 lowers the voltage of the control signal BLC1 toVblc and lowers the voltage of the control signal BLC2 to Vss, afterperforming the kick operation for each of the control signals BLC1 andBLC2. When the voltage of the control signal BLC2 becomes Vss, thetransistor 82 is turned off.

Next, at time t3, for example, the sequencer 13 raises the voltage ofthe control signal BLX1 from Vblc to Vblx, and lowers the voltage of thecontrol signal BLX2 from Vblx to Vss. When the voltage of the controlsignal BLC2 becomes Vss, the transistor 84 is turned off.

At this time, a voltage due to a path passing through the transistors50, 80, and 81 is applied to the bit line BL. Then, a voltage based onVblc is applied to the bit line BL, corresponding to the control signalBLC1, for example.

Further, while the read voltage AR is applied to the selected word lineWLsel, the voltage of the bit line BL changes according to the state ofthe selected memory cell, as in the first embodiment.

Next, at time t4, the sequencer 13 raises the voltage of the controlsignal BLC2 to Vxxl, for example. When the voltage of the control signalBLC2 rises to Vxxl, the transistor 82 is turned on. Then, the voltage ofthe node SEN changes according to the voltage of the bit line BL.

Then, after the voltage of the bit line BL is reflected on the node SEN,the sequencer 13 lowers the voltage of the control signal BLC2 to Vss.When the voltage of the control signal XXL falls to Vss, the transistor82 is turned off and the voltage of the node SEN is fixed.

Thereafter, the sequencer 13 asserts the control signal STB anddetermines the data to be stored in the selected memory cell.Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage AR, and stores the determination resultin the latch circuit ADL, for example.

Next, at time t5, the read voltage ER is applied to the selected signalline CGsel. At this time, similarly to the first embodiment, thesequencer 13 executes the kick operation for the selected signal lineCGsel. Then, similarly to the first embodiment, the voltage of theselected word line WLsel rises, based on the voltage applied to theselected signal line CGsel.

Further, at time t5, for example, the sequencer 13 lowers the voltage ofthe control signal BLX1 from Vblx to Vblc, raises the voltage of thecontrol signal BLX2 from Vss to Vblx, and raises the voltage of thecontrol signal BLC2 from Vss to Vblc. When the voltage of the controlsignal BLX2 becomes Vblx, the transistor 84 is turned on. When thevoltage of the control signal BLC2 becomes Vblc, the transistor 82 isturned on.

At time t5, the sequencer 13 controls the voltage of the bus LBUS, basedon the data stored in the latch circuit ADL. For example, when the latchcircuit ADL stores data corresponding to the off-cell, the sequencer 13sets the voltage of the bus LBUS to “L” level. When the latch circuitADL stores data corresponding to the on-cell, the sequencer 13 sets thevoltage of the bus LBUS to “H” level.

Then, the sense amplifier unit SAU corresponding to the selected memorycell which maintains the off state by the read voltage AR applies avoltage by a path passing through the transistors 50, 80, and 81 and avoltage by a path passing through the transistors 83, 84, 82, and 81, tothe corresponding bit line BL, respectively.

The sense amplifier unit SAU corresponding to the selected memory cellturned on by the read voltage AR applies a voltage by a path passingthrough the transistors 50, 80, and 81. In this way, in the readoperation in the second embodiment, the number of paths for applying avoltage to the bit line BL is changed based on the last read result.

Next, at time t6, the sequencer executes the kick operation for each ofthe control signals BLC1 and BLC2, for example. Specifically, similarlyto the time t2, the sequencer 13 raises the voltage of the controlsignal BLC1 to the kick voltage VblkH, and raises the voltage of thecontrol signal BLC2 to the kick voltage Vblk.

When at time t6, the voltage of the bus LBUS is “H” level, a voltage dueto a path passing through the transistors 50, 80, and 81 is applied tothe bit line BL. Then, a voltage based on Vblc is applied to the bitline BL, corresponding to the control signal BLX1, for example (“BLC1”in FIG. 16).

When at time t6, the voltage of the bus LBUS is “L” level, a voltage dueto a path passing through the transistors 50, 80, and 81 and a voltagedue to a path passing through the transistors 83, 84, 82, and 81 areapplied to the bit line BL. Then, a voltage based on the kick voltageVblk is applied to the bit line BL for a short time, corresponding tothe control signal BLC2, for example (“BLC2” in FIG. 16).

Next, at time t7, for example, the sequencer 13 raises the voltage ofthe control signal BLX1 from Vblc to Vblx, and lowers the voltage of thecontrol signal BLX2 from Vblx to Vss. When the voltage of the controlsignal BLC2 becomes Vss, the transistor 84 is turned off.

At this time, a voltage due to a path passing through the transistors50, 80, and 81 is applied to the bit line BL. Then, a voltage based onVblc is applied to the bit line BL, corresponding to the control signalBLC1, for example.

Further, while the read voltage ER is applied to the selected word lineWLsel, the voltage of the bit line BL changes according to the state ofthe selected memory cell, as in the first embodiment.

Next, at time t8, the sequencer 13 raises the voltage of the controlsignal BLC2 from Vss to Vxxl, for example. When the voltage of thecontrol signal BLC2 rises to Vxxl, the transistor 82 is turned on. Then,the voltage of the node SEN changes according to the voltage of the bitline BL, that is, the state of the selected memory cell.

Then, after the voltage of the bit line BL is reflected on the node SEN,the sequencer 13 lowers the voltage of the control signal BLC2, forexample, from Vxxl to Vss. When the voltage of the control signal BLC2falls to Vss, the transistor 82 is turned off and the voltage of thenode SEN is fixed.

Thereafter, the sequencer 13 asserts the control signal STB anddetermines the data to be stored in the selected memory cell.Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage ER.

Then, the sequencer 13 determines the lower page data based on thedetermination result and the read result based on the read voltage ARstored in the latch circuit ADL, and supplies the determined lower pagedata to, for example, the latch circuit XDL.

Next, at time t9, the sequencer 13 returns each of the selected signalline CGsel, and the control signals BLX1, BLX2, BLC1, and BLC2 to thestate before the read operation, and finishes the read operation of thelower page data. When the memory controller 2 detects that thesemiconductor memory 1 completes the read operation of the lower pagedata, the memory controller 2 causes the semiconductor memory 1 tooutput the lower page data.

As described above, the semiconductor memory 1 according to the secondembodiment can execute the read operation of the lower page data.Incidentally, in the semiconductor memory 1 according to the secondembodiment, in the read operation of each of the middle page data andthe upper page data, similarly to the read operation of the lower pagedata, the kick operation can be appropriately executed according to theread result.

[2-3] Effect of Second Embodiment

In the semiconductor memory 1 according to the second embodiment,similarly to the first embodiment, it is possible to omit the kickoperation for the bit line BL that can be determined to be in an onstate in advance. As a result, in the semiconductor memory 1 accordingto the second embodiment, it is possible to obtain the same effects asthose of the first embodiment.

In the semiconductor memory 1 according to the second embodiment, theroles of the two transistors 54 and 58 in the first embodiment areachieved by one transistor 82.

As a result, in the semiconductor memory 1 according to the secondembodiment, the number of elements in the sense amplifier unit SAU canbe made smaller than that in the first embodiment. Therefore, in thesemiconductor memory 1 according to the second embodiment, the circuitarea of the sense amplifier unit SAU can be reduced as compared with thefirst embodiment, and the chip area of the semiconductor memory 1 can bekept small.

The semiconductor memory 1 according to the second embodiment omits thekick operation in the first read process for all the bit lines BL. Thus,similarly to the first embodiment, in the semiconductor memory 1according to the second embodiment, it is possible to reduce the numberof error bits and improve the reliability of data.

Further, in the semiconductor memory 1 according to the secondembodiment, similar to the first embodiment, in the second andsubsequent read processes, the sequencer 13 may execute a kick operationfor the bit line BL corresponding to the memory cell transistor MT ofwhich being turned on is not clear, according to the read voltage to beapplied.

[2-4] Modification Example of Second Embodiment

In the semiconductor memory 1 according to the second embodimentdescribed above, the read operation in which read voltages are appliedin order from the lowest read voltage is given as an example, but thepresent disclosure is not limited thereto. For example, similarly to themodification example of the first embodiment, the operation described inthe second embodiment can be applied, even in the case where the readvoltage is applied from the highest read voltage.

Hereinafter, an example of a read operation in the modification exampleof the second embodiment will be described.

FIG. 17 illustrates an example of a timing chart in the read operationof the lower page data in the modification example of the secondembodiment.

As illustrated in FIG. 17, in the read operation in the modificationexample of the first embodiment, the order in which the read voltage isapplied is switched for the read operation in the first embodimentdescribed with reference to FIG. 16.

That is, in the read operation of the modification example of the secondembodiment, at time t1, the read voltage ER is applied to the selectedsignal line CGsel. At time t5, the read voltage AR is applied to theselected signal line CGsel. Then, the voltage of the selected word lineWLsel falls, based on the voltage of the selected signal line CGsel,similarly to the modification example of the first embodiment.

In the read operation in the modification example of the secondembodiment, similar to the modification example of the first embodiment,in the first kick operation, the kick operation for all the bit lines BLis executed.

Specifically, at time t1, the sequencer 13 sets the voltage of the busLBUS to “L” level. When the voltage of the bus LBUS is “L” level, thetransistor 83 is turned on. That is, each of a voltage due to a pathpassing through the transistors 50, 80, and 81 and a voltage due to apath passing through the transistors 83, 84, 82, and 81 is applied tothe bit line BL. Therefore, at time t2, a voltage based on the kickvoltage Vblk is applied to the bit line BL, corresponding to the controlsignal BLC2, for example.

Since the other operations of the read operation in the modificationexample of the second embodiment are similar to the read operation inthe second embodiment, a description thereof will be omitted. While theread operation of the lower page data is shown as the modificationexample of the second embodiment, the same operation may be executed forthe read operation of each of the middle page data and the upper pagedata.

According to the semiconductor memory 1 in the modification example ofthe second embodiment described above, in the read operation, similarlyto the modification example of the first embodiment, it is possible toexecute the kick operation for the bit line BL that can be determined tobe in an off state in advance. As a result, in the read operation in themodification example of the second embodiment, it is possible to obtainthe same effect as in the modification example of the first embodiment.

In the read operation in the modification example of the secondembodiment, similar to the modification example of the first embodiment,the kick operation in the first read process is executed for all the bitlines BL. Thus, in the read operation in the modification example of thesecond embodiment, similar to the modification example of the firstembodiment, it is possible to reduce the number of error bits andimprove the reliability of data.

Further, in the read operation in the modification example of the secondembodiment, similar to the modification example of the first embodiment,in the second and subsequent read processes, a kick operation may beomitted for the bit line BL corresponding to the memory cell transistorMT of which being turned on is not clear, according to the read voltageto be applied.

[3] Third Embodiment

The semiconductor memory 1 according to the third embodiment has acircuit configuration of the sense amplifier module 16 different from inthe first and second embodiments. In the semiconductor memory 1according to the third embodiment, in the read operation, whether or nota kick operation is to be executed is set for each read voltage. Withrespect to a semiconductor memory 1 according to the third embodiment,different features from those of the first and second embodiments willbe described below.

[3-1] Circuit Configuration of Sense Amplifier Module 16

FIG. 18 illustrates an example of the circuit configuration of the senseamplifier module 16 in the semiconductor memory according to the thirdembodiment, by extracting one sense amplifier unit SAU out of aplurality of sense amplifier units SAU in the sense amplifier module 16.

As illustrated in FIG. 18, a sense amplifier unit SA in the thirdembodiment has a configuration in which transistors 51 to 55, and 58 areomitted from the sense amplifier unit SA described with reference toFIG. 11 in the first embodiment and transistors 90 to 93 are addedthereto.

Each of the transistors 90 to 93 is, for example, an n-channel MOStransistor.

One end of the transistor 90 is connected to the other end of thetransistor 50. The other end of the transistor 90 is connected to thenode ND2. A control signal BLX is input to the gate of the transistor90.

The transistor 91 is connected to one end of the transistor 57 and thenode ND2. Specifically, one end of the transistor 91 is connected to thenode ND2, and the other end of the transistor 91 is connected to one endof the transistor 57. A control signal BLC is input to the gate of thetransistor 91.

One end of the transistor 92 is connected to the other end of thetransistor 50. The other end of the transistor 92 is connected to thenode SEN.

A control signal HLL is input to the gate of the transistor 92.

One end of the transistor 93 is connected to the node SEN. The other endof the transistor 93 is connected to the node ND2. A control signal XXLis input to the gate of the transistor 93.

Since the other configurations of the semiconductor memory 1 accordingto the third embodiment are similar to, for example, the semiconductormemory 1 according to the first embodiment, the explanation is omitted.

[3-2] Read Operation of Semiconductor Memory 1

Read Operation in Comparative Example of Third Embodiment

Before explaining the read operation of the semiconductor memory 1according to the third embodiment, the read operation in the comparativeexample of the third embodiment is explained. In the read operation inthe comparative example of the third embodiment, in the read processcorresponding to the all the read voltages, the kick operation for thecontrol signal BLC is executed.

FIG. 19 illustrates an example of a timing chart in the read operationof the middle page data in the comparative example of the thirdembodiment. In the read operation in the comparative example of thethird embodiment, it is defined that the transistor 50 is in an on statesimilarly to the first embodiment and supplies a voltage to thetransistors 90 and 92.

In a comparative example of the third embodiment, it is assumed that thecontrol signal HLL is properly controlled by the sequencer 13 and thetransistor 92 properly charges the node SEN. It is assumed that thevoltages of the selected word line WLsel and the bit line BL changeaccording to the voltages of the selected signal line CGsel and thecontrol signal BLC, respectively, similarly to the first embodiment.

As illustrated in FIG. 19, at the start of the read operation, therespective voltages of the selected signal line CGsel, the selected wordline WLsel, the control signal BLX, BLC, and XXL are, for example, aground voltage Vss. The voltage of the control signal STB is, forexample, “L” level.

When the read operation of the middle page data is started, thesequencer 13 executes an operation of removing residual electrons in thechannel, for example, in the period from the time t0 to the time t1,similarly to the first embodiment. In the period from the time t1 to thetime t4, the sequencer 13 executes a read process using the read voltageBR. In the period from the time t4 to the time t7, the sequencer 13executes a read process using the read voltage DR. In the period fromthe time t7 to the time t10, the sequencer 13 executes a read processusing the read voltage FR.

Specifically, at time t0, for example, the read pass voltage Vread isapplied to the selected signal line CGsel. Then, the voltage of theselected word line WLsel rises based on the voltage applied to theselected signal line CGsel.

Further, at time t0, for example, the sequencer 13 raises the voltage ofthe control signal BLX from Vss to VblxL, and raises the voltage of thecontrol signal BLC from Vss to VblcL. At this time, the voltage clampedby the transistors 90 and 91, for example, is applied to the bit lineBL.

Next, at time t1, the read voltage BR is applied to the selected signalline CGsel. Then, the voltage of the selected word line WLsel fallsbased on the voltage applied to the selected signal line CGsel. Further,at time t1, the sequencer 13 raises the voltage of the control signalBLX from VblxL to Vblc, for example.

Next, at time t2, the sequencer 13 executes the kick operation for thecontrol signal BLC. Specifically, the kick voltage Vblk is first appliedto the signal line to which the control signal BLC is supplied, and Vblcis applied after the kick voltage Vblk is applied for a short time.

Further, while the read voltage BR is applied to the selected word lineWLsel, the voltage of the bit line BL changes according to the state ofthe selected memory cell, as in the first embodiment.

Next, at time t3, the sequencer 13 raises the voltage of the controlsignal XXL from. Vss to Vxxl. When the voltage of the control signal XXLrises to Vxxl, the transistor 93 is turned on. Then, the voltage of thenode SEN changes according to the voltage of the bit line BL, that is,the state of the selected memory cell.

Then, after the voltage of the bit line BL is reflected on the node SEN,the sequencer 13 lowers the voltage of the control signal XXL from Vxxlto Vss. When the voltage of the control signal XXL falls to Vss, thetransistor 93 is turned off and the voltage of the node SEN is fixed.

Thereafter, the sequencer 13 asserts the control signal STB anddetermines the data to be stored in the selected memory cell.Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage BR, and stores the determination resultin the latch circuit ADL, for example.

Next, at time t4, the read voltage DR is applied to the selected signalline CGsel. At this time, similarly to the first embodiment, thesequencer 13 executes the kick operation for the selected signal lineCGsel. Then, similarly to the first embodiment, the voltage of theselected word line WLsel rises, based on the voltage applied to theselected signal line CGsel.

Next, at time t5, the sequencer 13 executes the kick operation for thecontrol signal BLC. Since the operation of the semiconductor memory 1 atthe time t5 is similar to the operation at the time t2, the explanationis omitted. While the read voltage DR is applied to the selected wordline WLsel, the voltage of the bit line BL changes according to thestate of the selected memory cell.

Next, at time t3, the sequencer 13 controls the control signal XXLsimilarly to the time t3, and reflects the voltage of the bit line BL onthe voltage of the node SEN. Thereafter, the sequencer 13 asserts thecontrol signal STB and determines the data to be stored in the selectedmemory cell.

Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage ER. The sequencer 13 performs thecalculation based on the above determination result and thedetermination result of the read voltage BR stored in the latch circuitADL, and stores an operation result, for example, in the latch circuitBDL.

Next, at time t7, the read voltage FR is applied to the selected signalline CGsel. At this time, similarly to the first embodiment, thesequencer 13 executes the kick operation for the selected signal lineCGsel. Then, similarly to the first embodiment, the voltage of theselected word line WLsel rises, based on the voltage applied to theselected signal line CGsel.

Next, at time t8, the sequencer 13 executes the kick operation for thecontrol signal BLC. Since the operation of the semiconductor memory 1 atthe time t8 is similar to the operation at the time t2, the explanationis omitted. While the read voltage FR is applied to the selected wordline WLsel, the voltage of the bit line BL changes according to thestate of the selected memory cell.

Next, at time t9, the sequencer 13 controls the control signal XXLsimilarly to the time t3, and reflects the voltage of the bit line BL onthe voltage of the node SEN. Thereafter, the sequencer 13 asserts thecontrol signal STB and determines the data to be stored in the selectedmemory cell.

Specifically, the sense amplifier unit SAU determines whether or not thethreshold voltage of the corresponding selected memory cell is equal toor higher than the read voltage FR. Then, the sequencer 13 determinesthe middle page data based on the determination result and thedetermination result based on the read voltages BR and DR stored in thelatch circuit BDL, and supplies the determined middle page data to, forexample, the latch circuit XDL.

Next, at time t10, the sequencer 13 returns each of the selected signalline CGsel, and the control signals BLX, BLC, and XXL to the statebefore the read operation, and finishes the read operation of the middlepage data. When the memory controller 2 detects that the semiconductormemory 1 completes the read operation of the middle page data, thememory controller 2 causes the semiconductor memory 1 to output thelower page data.

Read Operation in Third Embodiment

For the read operation in the comparative example of the thirdembodiment described above, in the read operation in the thirdembodiment, whether or not to execute the kick operation for the controlsignal BLC is set for each read voltage.

FIG. 20 illustrates an example of the condition of the kick operation inthe read operation of a semiconductor memory according to the thirdembodiment.

As illustrated in FIG. 20, the sequencer 13 omits the kick operation forthe control signal BLC, in each of read processes corresponding to theread voltages AR, BR, and CR, for example. Further, the sequencer 13executes the kick operation for the control signal BLC, in each of readprocesses corresponding to the read voltages DR, ER, FR, and GR, forexample.

In other words, the semiconductor memory 1 according to the thirdembodiment is divided into, for example, two groups of a group having alow read voltage (for example, the read voltages AR, BR, and CR) and agroup having a high read voltage (for example, the read voltages DR, ER,FR, and GR). Then, the sequencer 13 omits a kick operation for thecontrol signal BLC in a group having a low read voltage and executes thekick operation in a group having a high read voltage.

Incidentally, in the read operation, the setting of whether or not toexecute the kick operation for the control signal BLC is not limited tothe grouping described above, and may be changed to any setting.

FIG. 21 illustrates an example of a timing chart in the read operationof the middle page data in the semiconductor memory 1 according to thethird embodiment.

As illustrated in FIG. 21, in the read operation in the thirdembodiment, the kick operation corresponding to the read voltage BR isomitted from the read operation in the comparative example in the thirdembodiment described with reference to FIG. 19.

Specifically, at time t2, the sequencer 13 does not raise the voltage ofthe control signal BLC to the kick voltage Vblk and raises to Vblc.Therefore, at time t2, a voltage based on Vblc is applied to the bitline BL, corresponding to the control signal BLC, for example. Since theother operations of the read operation in the third embodiment aresimilar to the read operation in the comparative example of the thirdembodiment, a description thereof will be omitted.

As described above, the semiconductor memory 1 according to the thirdembodiment can execute the read operation of the middle page data.Incidentally, in the semiconductor memory 1 according to the thirdembodiment, in the read operation of each of the lower page data and theupper page data, similarly to the read operation of the middle pagedata, the kick operation can be appropriately executed for each readvoltage.

[3-3] Effect of Third Embodiment

For example, it is considered that the number of memory cell transistorsMT to be turned on by a low read voltage is smaller than the number ofmemory cell transistors MT to be turned on by a high read voltage.

In other words, it is considered that the number of memory celltransistors MT to be turned off by a low read voltage is larger than thenumber of memory cell transistors MT to be turned off by a high readvoltage.

As described above, in the read operation, whether the number ofon-cells is dominant or the number of off-cells is dominant may beassumed from the value of the read voltage. That is, the number ofoff-cells affected by noise by the bit line BL connected to the on-cellmay be assumed, based on the relationship between the number of on-cellsand the number of off-cells.

Therefore, in the semiconductor memory 1 according to the thirdembodiment, whether or not to execute the kick operation for the bitline BL is set for each read voltage. Specifically, the sequencer 13omits the kick operation in the group having a low read voltage (forexample, the read voltages AR, BR, and CR), and executes the kickoperation in the group having a high read voltage (for example, the readvoltages DR, ER, FR, and GR).

That is, the sequencer 13 omits the kick operation, in the read processof a group which is estimated that the number of off-cells is dominantand the number of memory cells capable of causing erroneous readingcaused by the kick operation is large. On the other hand, the sequencer13 executes the kick operation, in the read process of a group which isestimated that the number of on-cells is dominant and the number ofmemory cells capable of causing erroneous reading caused by the kickoperation is small.

As described above, in the semiconductor memory 1 according to the thirdembodiment, an appropriate read process can be executed in each of agroup having a high read voltage and a group having a low read voltage.As a result, similarly to the first embodiment, in the semiconductormemory 1 according to the third embodiment, it is possible to reduce thenumber of error bits and improve the reliability of data.

[3-4] Modification Example of Third Embodiment

In the semiconductor memory 1 according to the third embodimentdescribed above, the read operation in which read voltages are appliedin order from the lowest read voltage is given as an example, but thepresent disclosure is not limited thereto. For example, similarly to themodification example of the first embodiment, the operation described inthe third embodiment can be applied, even in the case where the readvoltage is applied from the highest read voltage.

Hereinafter, an example of a read operation in the modification exampleof the third embodiment will be described.

FIG. 22 illustrates an example of a timing chart in the read operationof the middle page data in the modification example of the thirdembodiment.

As illustrated in FIG. 22, in the read operation in the modificationexample of the third embodiment, the order in which the read voltage isapplied is switched for the read operation in the third embodimentdescribed with reference to FIG. 21.

That is, in the read operation of the modification example of the thirdembodiment, at time t1, the read voltage FR is applied to the selectedsignal line CGsel. At time t4, the read voltage DR is applied to theselected signal line CGsel. At time t7, the read voltage BR is appliedto the selected signal line CGsel. Then, the voltage of the selectedword line WLsel falls, based on the voltage of the selected signal lineCGsel, similarly to the modification example of the first embodiment.

Further, in the modification example of the third embodiment, similar tothe read operation in the third embodiment, the sequencer 13 executesthe read operation, based on the setting of the kick operation for thecontrol signal BLC shown in FIG. 20.

Specifically, for example, in the read operation of the middle page, thesequencer 13 executes a kick operation in the read process using each ofthe read voltages FR and DR, and omits a kick operation in the readprocess using the read voltage BR.

Since the other operations of the read operation in the modificationexample of the third embodiment are similar to the read operation in thethird embodiment, a description thereof will be omitted. While the readoperation of the middle page data is shown as the modification exampleof the third embodiment, the same operation may be executed for the readoperation of each of the lower page data and the upper page data.

As described above, in the read operation in the modification example ofthe third embodiment, similar to the third embodiment, an appropriateread process may be executed in each of a group having a high readvoltage and a group having a low read voltage. As a result, in the readoperation in the modification example of the third embodiment, it ispossible to obtain the same effect as in the third embodiment.

[4] Fourth Embodiment

A semiconductor memory 1 according to a fourth embodiment has the sameconfiguration as that of the third embodiment. In the semiconductormemory 1 according to the fourth embodiment, a kick amount is changedfor each read voltage. With respect to a semiconductor memory 1according to a fourth embodiment, different features from those of thefirst to third embodiments will be described below.

[4-1] Read Operation of Semiconductor Memory 1

FIG. 23 illustrates an example of the condition of the kick operation inthe read operation of a semiconductor memory according to the fourthembodiment.

As illustrated in FIG. 23, for example, similar to the third embodiment,the sequencer 13 omits a kick operation for the control signal BLC, ineach of the read processes corresponding to the read voltages AR, BR,and CR, and executes a kick operation for the control signal BLC, ineach of the read processes corresponding to the read voltages DR, ER,FR, and GR.

In the fourth embodiment, in the kick operation for the control signalBLC, for example, the sequencer 13 applies a small kick amountcorresponding to each of the read voltages DR and ER, and applies alarge kick amount corresponding to each of the read voltages FR and GR.

Incidentally, in the read operation, each of the setting of whether ornot to execute the kick operation for the control signal BLC and thesetting of the kick amount may be changed to any setting. The setting ofthe kick amount is not limited to two types of “large” or “small”, andthree or more settings may be used.

FIG. 24 illustrates an example of a timing chart in the read operationof the middle page data in the semiconductor memory 1 according to thefourth embodiment.

As illustrated in FIG. 24, in the read operation in the fourthembodiment, similar to the read operation in the third embodimentdescribed with reference to FIG. 21, the kick operation in the readprocess using the read voltage FR at time t2 is omitted.

Then, the read operation in the fourth embodiment is different from theread operation in the third embodiment in the kick voltages in the readprocess using the read voltage DR and the read process using the readvoltage FR.

Specifically, at time t5, the sequencer 13 executes a kick operationcorresponding to the read voltage DR. At this time, the kick voltageVblk1 is first applied to the signal line to which the control signalBLC is supplied, and Vblc is applied after the kick voltage Vblk1 isapplied for a short time. The kick voltage Vblk1 is higher than Vblc,and the difference between Vblk1 and Vblc corresponds to the kick amountDblk1.

At time t8, the sequencer 13 executes a kick operation corresponding tothe read voltage FR. At this time, the kick voltage Vblk2 is firstapplied to the signal line to which the control signal BLC is supplied,and Vblc is applied after the kick voltage Vblk2 is applied for a shorttime. The kick voltage Vblk2 is higher than Vblk1, and a differencebetween Vblk2 and Vblc corresponds to the kick amount Dblk2.

As illustrated above, in the fourth embodiment, the kick amount Dblk2 ofthe kick voltage Vblk2 is set larger than the kick amount Dblk1 of thekick voltage Vblk1. Therefore, the voltage applied to the bit line BL bythe kick operation at the time t8 is higher than the voltage applied tothe bit line BL by the kick operation at the time t5. Since the otheroperations of the read operation in the fourth embodiment are similar tothe read operation in the third embodiment, a description thereof willbe omitted.

As described above, the semiconductor memory 1 according to the fourthembodiment can execute the read operation of the middle page data.Incidentally, in the semiconductor memory 1 according to the fourthembodiment, in the read operation of each of the lower page data and theupper page data, similarly to the read operation of the middle pagedata, the kick operation can be appropriately executed for each readvoltage, and the kick operation can be appropriately changed for eachread voltage.

[4-2] Effect of Fourth Embodiment

It may be assumed that an appropriate kick amount in the read operationis different depending on the read voltage of the read process in whichthe kick operation is executed.

For example, since the memory cell with a high threshold voltage isunlikely to be turned on, it may be assumed that it is preferable toapply a high kick amount when a kick operation is applied. On the otherhand, since the memory cell with a low threshold voltage tends to berelatively easily turned on, it may be assumed that it is preferable toapply a low kick amount when a kick operation is applied.

Therefore, in the semiconductor memory 1 according to the fourthembodiment, whether or not to execute the kick operation for the bitline BL is set for each read voltage, as in the third embodiment. In thefourth embodiment, in a case where the kick operation for the bit lineBL is executed, the kick amount is changed based on the correspondingread voltage.

Thus, in the semiconductor memory 1 according to the fourth embodiment,an appropriate kick amount may be applied for each read process. Thatis, in the semiconductor memory 1 according to the fourth embodiment, itis possible to prevent an increase in the number of error bits caused byperforming a kick operation for the bit line BL connected to theon-cell. As a result, in the semiconductor memory 1 according to thefourth embodiment, it is possible to reduce the number of error bits ascompared to the third embodiment, and improve the reliability of data.

[4-3] Modification Example of Fourth Embodiment

In the semiconductor memory 1 according to the fourth embodimentdescribed above, the read operation in which read voltages are appliedin order from the lowest read voltage is given as an example, but thepresent disclosure is not limited thereto. For example, similarly to themodification example of the first embodiment, the operation described inthe fourth embodiment may be applied, even in the case where the readvoltage is applied from the highest read voltage.

Hereinafter, an example of a read operation in the modification exampleof the fourth embodiment will be described.

FIG. 25 illustrates an example of a timing chart in the read operationof the middle page data in the modification example of the fourthembodiment.

As illustrated in FIG. 25, in the read operation in the modificationexample of the fourth embodiment, the order in which the read voltage isapplied is switched for the read operation in the fourth embodimentdescribed with reference to FIG. 24.

That is, in the read operation of the modification example of the fourthembodiment, at time t1, the read voltage FR is applied to the selectedsignal line CGsel. At time t4, the read voltage DR is applied to theselected signal line CGsel. At time t7, the read voltage BR is appliedto the selected signal line CGsel. Then, the voltage of the selectedword line WLsel falls, based on the voltage of the selected signal lineCGsel, similarly to the modification example of the first embodiment.

Further, in the modification example of the fourth embodiment, similarto the read operation in the fourth embodiment, the sequencer 13executes the read operation, based on the setting of the kick operationfor the control signal BLC shown in FIG. 23.

Specifically, for example, in the read operation of the middle page, thesequencer 13 executes the kick operation to which the kick amount Dblk2is applied, in the read process using the read voltage FR. In the readprocess using the read voltage DR, the sequencer 13 executes the kickoperation to which the kick amount Dblk1 is applied. In the read processusing the read voltage BR, the sequencer 13 omits the kick operation.

Since the other operations of the read operation in the modificationexample of the fourth embodiment are similar to the read operation inthe fourth embodiment, a description thereof will be omitted. While theread operation of the middle page data is shown as the modificationexample of the fourth embodiment, the same operation may be executed forthe read operation of each of the lower page data and the upper pagedata.

As described above, in the read operation in the modification example ofthe fourth embodiment, similar to the fourth embodiment, an appropriateread process can be executed in each of a group having a high readvoltage and a group having a low read voltage. As a result, in the readoperation in the modification example of the fourth embodiment, it ispossible to obtain the same effect as in the fourth embodiment.

[5] Other Modification Examples

The semiconductor memory of embodiments includes first and second memorycells, word lines, first and second bit lines, first and second senseamplifiers, and a controller. Each of the first and second memory cellsstores a plurality of bits of data based on a threshold voltage. Theword lines are connected to the respective gates of the first and secondmemory cells. The first and second bit lines are connected to the firstand second memory cells, respectively. The first and second senseamplifiers are connected to the first and second bit lines,respectively. Each of the first and second sense amplifiers includes afirst transistor, a second transistor, and a third transistor. One endof the third transistor is electrically connected to each of the firsttransistor and the second transistor, and the other end is connected tothe corresponding bit line. In the read operation of the first andsecond memory cells, the controller applies a first read voltage to theword line at a first time <for example, in FIG. 13, t5> in a firstperiod when the controller applies the first read voltage, thecontroller applies a first voltage <for example, in FIG. 13, Vblk>higher than a ground voltage to the first transistor, and applies asecond voltage <for example, in FIG. 13, Vblc> different from the firstvoltage to the second transistor. At the first time, the first senseamplifier applies a voltage to the first bit line via the firsttransistor and the third transistor, the second sense amplifier appliesa voltage to the second bit line via the second transistor and the thirdtransistor. Thus, in the semiconductor memory according to theembodiment, it is possible to speed up the read operation.

In the first embodiment, the case where the kick amount in the kickoperation is uniform is given as an example, but the present disclosureis not limited thereto. For example, in the read operation of thesemiconductor memory 1 according to the first embodiment, but as in thefourth embodiment, a different kick amount may be applied for eachcorresponding read voltage. This read operation is referred to as afirst modification example, and will be described below.

FIG. 26 illustrates an example of a timing chart in the read operationof the lower page data in the first modification example. As illustratedin FIG. 26, the read operation in the first modification example isdifferent from the read operation described with reference to FIG. 13 inthe first embodiment in that the kick amount of the control signal BLCat time t2 is different from the kick amount of the control signal BLCat time t5.

Specifically, in the read operation in the first modification example,the kick amount Dblk1 is applied in the kick operation at time t2, andthe voltage of the control signal BLC1 temporarily rises to Vblk1. Inthe kick operation at time t5, the kick amount Dblk2 greater than thekick amount Dblk1 is applied, and the voltage of the control signal BLC1temporarily rises to Vblk2.

Thus, in the read operation in the first modification example, similarto the fourth embodiment, an appropriate kick amount may be applied foreach read process. Further, even in a case where the read voltage isapplied from the highest read voltage as in the modification example ofthe first embodiment, similar to the fourth embodiment, an appropriatekick amount may be applied for each read process.

Further, in the second embodiment, the case where the kick amount in thekick motion is uniform is given as an example, but as in the fourthembodiment, a different kick amount may be applied for eachcorresponding read voltage. This read operation is referred to as asecond modification example, and will be described below.

FIG. 27 illustrates an example of a timing chart in the read operationof the lower page data in the second modification example. Asillustrated in FIG. 27, the read operation in the second modificationexample is different from the read operation described with reference toFIG. 16 in the second embodiment in that the kick amount of the controlsignal BLC2 at time t2 is different from the kick amount of the controlsignal BLC2 at time t6.

Specifically, in the read operation in the second modification example,in the kick operation at time t2, the voltage of the control signal BLC2temporarily rises to Vblk1. In the kick operation at time t6, the kickamount larger than the kick amount at time t2 is applied, and thevoltage of the control signal BLC1 temporarily rises to Vblk2.

Thus, in the read operation in the second modification example, similarto the fourth embodiment, an appropriate kick amount may be applied foreach read process. Further, even in a case where the read voltage isapplied from the highest read voltage as in the modification example ofthe second embodiment, similar to the fourth embodiment, an appropriatekick amount may be applied for each read process.

In the above embodiment, the case where the kick amount applied in thekick operation for the selected signal line CGsel is constant isdescribed, but the present disclosure is not limited to this. Forexample, the kick amount corresponding to the selected signal line CGselmay be changed for each read voltage.

The timing chart used for explaining the read operation in the aboveembodiments is only an example. For example, the timing at which thevoltage of each of the signal and the wiring at each time is controlledmay be shifted. In the read operation, at least the front and rearrelationships of the operation at each time may not be switched.

In the read operation described in the above embodiments, the case wherean operation to remove residual electrons in the channel is insertedbefore the read process is executed is given as an example, but thepresent disclosure is not limited to this. In the read operation, theoperation of removing residual electrons in the channel may be omitted.

The read operation described in the above embodiments may also beapplied to a verify read in a write operation. Even in a case where theabove embodiments are applied to the verify read, the semiconductormemory 1 can bring about the same effect as the above embodiment.

In the first embodiment, the case where whether or not the kickoperation is applied to the bit line BL is controlled by the node INV(ADL) of the latch circuit ADL is given as an example, but the presentdisclosure is not limited thereto. For example, as in the secondembodiment, the bus LBUS may be used. In this case, the bus LBUS isconnected to the gate of each of the transistor 52 and transistor 53.

Similarly, in the second embodiment, the case where whether or not thekick operation is applied to the bit line BL is controlled by the busLBUS is given as an example, but the present disclosure is not limitedto this. For example, as in the first embodiment, the node INV (ADL) ofthe latch circuit ADL may be used. In this case, the gate of thetransistor 83 is connected to the node INV (ADL).

In the above embodiment, the case where the voltage of the selected wordline WLsel becomes the same voltage as the voltage of the selectedsignal line CGsel is given as an example, but the present disclosure isnot limited thereto. The voltage of the selected word line WLsel may bedifferent from the voltage of the selected signal line CGsel, or may bechanged based on the change of the selected signal line CGsel.

In the above embodiment, the case where triple-level cell (TLC) isapplied as a method of storing data is given as an example, but thepresent disclosure is not limited thereto.

For example, even in a case where the memory cell transistor MT storesdata of 2 bits or 4 bits or more, the semiconductor memory 1 can executethe read operation described in the above embodiment.

In the above embodiment, the timing at which the kick operation isstarted may be set to any timing. The timing at which the kick operationis started may be included at least in a period from the start ofapplication of the corresponding read voltage to stabilization at theread voltage.

In the modification example of the above embodiment, the case where thekick operation for the selected signal line CGsel is omitted when theread voltage transitions from the higher value to the lower value isgiven as an example, but the present disclosure is not limited to this.For example, in a case where the read voltage transitions from thehigher value to the lower value, the kick operation for the selectedsignal line CGsel may be executed. In this case, the kick amount in thekick operation can be set to, for example, a negative value.

In the above embodiment, the case where the end portion of the word lineWL is formed in a stepwise shape with three rows in the extraction areaHA is given as an example, but the present disclosure is not limitedthereto. For example, the end portion of the word line WL may have astair structure of two rows or four or more rows.

In the above embodiment, the case where the directions in which thevoltages are applied to the blocks BLK arranged in the Y direction aredifferent between the even-numbered blocks BLK and the odd-numberedblocks BLK is given as an example, but the present disclosure is limitedto this. For example, the extraction area HA may be provided only on oneside in the X direction with respect to the cell area CA. In this case,a voltage is applied to the stacked wiring corresponding to each blockBLK from the same direction.

In the above embodiment, the case where the voltage is applied from oneside in the X direction with respect to the stacked wiring such as theword line WL is given as an example, but the present disclosure is notlimited thereto. For example, in a certain block BLK, a contact CC isprovided in each of the extraction areas HA1 and HA2, and a voltage maybe applied to the word line WL or the like from both sides in the Xdirection. Even in such a case, for example, the influence of the RCdelay may occur in the central portion of the word line WL, so the sameeffect can be obtained by applying any one of the above embodiments.

In the above embodiment, the circuit configuration of the senseamplifier module 16 may be variously changed. For example, the number oflatch circuits in the sense amplifier unit SAU can be appropriatelychanged based on the number of bits stored in one memory cell transistorMT. Depending on the configuration of the sense amplifier module 16, theoperation of “asserting the control signal STB” may correspond to thetemporary change of the control signal STB from the “H” level to the “L”level by the sequencer 13.

In the above embodiment, the memory pillar MP may have a structure inwhich a plurality of pillars are connected in the Z direction. Forexample, the memory pillar MP may have a structure in which a pillarpenetrating the conductor (the select gate line SGD) and a pillarpenetrating a plurality of conductors 23 (the word line WL) areconnected. Further, the memory pillar MP may have a structure in which aplurality of pillars each penetrating a plurality of conductors 23 areconnected in the Z direction.

In the above embodiment, the structure in which the slits SLT and SLTadivide the conductor 24 is given as an example, but the slits SLT andSLTa may not divide the conductor 24. In this case, the memory pillar MPhas a structure in which a plurality of pillars are connected in the Zdirection. For example, a pillar provided below penetrates theconductors 22 and 23, and a pillar provided above penetrates theconductor 24. Then, the conductor 24 is divided by, for example, slitsdifferent from the slits SLT and SLTa, and each of the divided pluralityof conductors 24 functions as a select gate line SGD.

In the semiconductor memory 1 according to the above embodiment, theconductors 23 and 24 may be formed by executing the replacement processusing the slits SLT, SLTa, and SLTb, for example. In this case, forexample, between the adjacent slits SLT and SLTb, a plurality of supportcolumns, each being formed of an insulator and penetrating the stackedstructure in which the conductors 23 and 24 are formed, may be formed.

In the above embodiment, the case where the semiconductor memory 1 has astructure in which the circuit such as the sense amplifier module 16 isprovided under the memory cell array 10 is given as an example, but thedisclosure is not limited thereto. For example, the semiconductor memory1 may have a structure in which the memory cell array 10 is formed onthe semiconductor substrate 20. In this case, in the memory pillar MP,for example, the semiconductor 31 is electrically connected to thesource line SL trough the lower surface of the memory pillar MP.

In the above embodiments, the structure of the memory cell array 10 maybe another structure. The other configurations of the memory cell array10 are described in, for example, U.S. patent application Ser. No.12/407,403 filed on Mar. 19, 2009, entitled “three-dimensional stackednonvolatile semiconductor memory”. It is described in U.S. patentapplication Ser. No. 12/406,524 filed on Mar. 18, 2009, entitled “athree-dimensional stacked nonvolatile semiconductor memory” and U.S.patent application Ser. No. 12/679,991 filed on Mar. 25, 2010, entitled“a nonvolatile semiconductor memory device and a method of manufacturingthe same”. It is described in U.S. patent application Ser. No.12/532,030 filed on Mar. 23, 2009, entitled “a semiconductor memory anda method of manufacturing the same”. These patent applications areincorporated herein by reference in its entirety.

In the above embodiments, the block BLK may not be an erase unit. Theother erase operations are described in U.S. patent application Ser. No.13/235,389 filed on Sep. 18, 2011, entitled “nonvolatile semiconductormemory device”, and U.S. patent application Ser. No. 12/694,690 filed onJan. 27, 2010, entitled “nonvolatile semiconductor memory device”. Thesepatent applications are incorporated herein by reference in itsentirety.

In the above embodiments, the case where the memory cell transistors MTprovided in the memory cell array 10 are three-dimensionally stacked isdescribed as an example, but the present disclosure is not limitedthereto. For example, the configuration of the memory cell array 10 maybe a plane NAND flash memory in which the memory cell transistors MT aretwo-dimensionally disposed.

In the present specification, the “connection” means that it iselectrically connected, and for example, it does not exclude thatanother element is interposed therebetween. Further, in the presentspecification, the “off state” means that a voltage less than thethreshold voltage of the transistor is applied to the gate of thecorresponding transistor, and for example, it does not exclude that aminute current such as a leak current of the transistor flows.

In the present specification, “the period during which the controllerapplies the read voltage” corresponds to, for example, in FIG. 13, theperiod from the time t1 to the time t4 corresponding to the read voltageAR and the period from the time t4 to the time t7 corresponding to theread voltage ER. That is, in the present specification, the periodincludes a time at which the application of the read voltage is startedand a period during which the kick operation is executed.

In the present specification, the word “conductivity type” is used todistinguish between an n-channel MOS transistor and a p-channel MOStransistor. For example, a transistor of a first conductivity typecorresponds to an n-channel MOS transistor, and a transistor of a secondconductivity type which is different from the first conductivity typecorresponds to a p-channel MOS transistor.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A semiconductor memory comprising: a plurality ofmemory cell transistors, a threshold voltage of each of the memory celltransistor being changeable to store multi-bit data; a word line whichis electrically connected to gates of the memory cell transistors; aplurality of bit lines which are electrically connected to one ends ofthe memory cell transistors, respectively; a source line which iselectrically connected to the other ends of the memory cell transistors;a plurality of sense amplifier units which are electrically connected tothe bit lines, respectively, each of the sense amplifier units includinga sense amplifier, a first latch, and a second latch; and a controller,wherein each of the sense amplifiers includes a first transistor havinga gate to which a first control signal is supplied, one end electricallyconnected to a corresponding one of the bit lines, and the other endelectrically connected to a first node, a second transistor having agate to which a second control signal is supplied and one endelectrically connected to the other end of the first transistor, a thirdtransistor having a gate to which a signal based on data stored in acorresponding one of the first latches is supplied, one end electricallyconnected to the other end of the second transistor, and the other endelectrically connected to a power supply node, a fourth transistorhaving a gate to which a third control signal is supplied and one endelectrically connected to the other end of the first transistor, and afifth transistor having a gate to which a signal based on data stored ina corresponding one of the second latches is supplied and one endelectrically connected to the other end of the fourth transistor.
 2. Thesemiconductor memory according to claim 1, wherein, in each of the senseamplifiers, each of the first latch and the second latch is a staticlatch.
 3. The semiconductor memory according to claim 1, wherein thememory cell transistors includes a first memory cell transistor and asecond memory cell transistor, and the bit lines includes a first bitline electrically connected to the one end of the first memory celltransistor and a second bit line electrically connected to the one endof the second memory cell transistor, and wherein the sense amplifiersincludes a first sense amplifier electrically connected to the first bitline and a second sense amplifier electrically connected to the secondbit line, and wherein, when the controller performs an operation, thefirst sense amplifier supplies a first voltage higher than a groundvoltage to the first bit line, and the second sense amplifier supplies asecond voltage lower than the first voltage and higher than the groundvoltage to the second bit line.
 4. The semiconductor memory according toclaim 3, wherein when the controller performs the operation, the firstsense amplifier supplies the first voltage to the first bit line throughthe first transistor and the second transistor, and the second senseamplifier supplies the second voltage to the second bit line through thefirst transistor and the fourth transistor.
 5. The semiconductor memoryaccording to claim 1, wherein each of the sense amplifiers furtherincludes a sixth transistor having a gate to which a signal based ondata stored in a corresponding one of the second latches is supplied,one end electrically connected to the other end of the secondtransistor, and the other end electrically connected to the other end ofthe fifth transistor, a seventh transistor having a gate to which afourth control signal is supplied, one end electrically connected to theother end of the fifth transistor and the other end of the sixthtransistor, and the other end electrically connected to the one end ofthe third transistor, and an eighth transistor having a gate to which afifth control signal is supplied, one end electrically connected to theother end of the fifth transistor and the other end of the sixthtransistor, and the other end electrically connected to a sense node. 6.The semiconductor memory according to claim 5, wherein a thresholdvoltage of the first memory cell transistor is set to be higher than athreshold voltage of the second memory cell transistor, and when thecontroller performs a read operation, at a first time of a first periodduring which the controller applies a first read voltage to the wordline, the controller sets the second control signal to a first voltagehigher than a ground voltage, and sets the third control signal to asecond voltage lower than the first voltage and higher than the groundvoltage, and the first sense amplifier applies a voltage to the firstbit line through the first transistor and the second transistor, and thesecond sense amplifier applies a voltage to the second bit line throughthe first transistor and the fourth transistor.
 7. The semiconductormemory according to claim 6, wherein at a second time in the firstperiod that is later than the first time, the controller sets the secondcontrol signal to the second voltage, and sets the third control signalto the second voltage.
 8. The semiconductor memory according to claim 7,wherein when the controller performs a read operation, the controllerapplies a second read voltage which is lower than the first read voltageto the word line, before applying the first read voltage to the wordline, and at a third time in a second period when the controller appliesthe second read voltage, the first sense amplifier applies a voltage tothe first bit line through the first transistor and the secondtransistor, and the second sense amplifier applies a voltage to thesecond bit line through the first transistor and the second transistor.9. The semiconductor memory according to claim 8, wherein during theread operation, the controller updates information stored in the secondlatch based on a reading result obtained during the second period.